Enemy Movement

In my game the enemies are supposed to follow the player without rotation on the X or Z axis. Would the best way to approach this be with a NavMeshAgent or a script with Vector3.MoveTowards?

I have tried before and this is what I have found. With the NavMeshAgent I get no error, but the enemy doesn't follow the player. When I tried using Vector3.MoveTowards, it didn't move the enemy. Here are both of my scripts:

Spoiler: NavMeshAgent Script

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class EnemyCraftAI : MonoBehaviour {
5.  
6.     public Transform target;
7.  
8.     public float attackDistance = 20.0f;
9.  
10.     public float attackDelay = 0.75f;
11.  
12.     public float effectsDisplayTime = 0.2f;
13.  
14.     public Transform gunEnd;
15.  
16.     public float shootRange = 20f;
17.  
18.     public int attackDamage = 10;
19.  
20.  
21.     float attackTimer;
22.  
23.     float distance;
24.  
25.     NavMeshAgent agent;
26.  
27.     EnemyHealth health;
28.  
29.     Ray shootRay;
30.     RaycastHit shootHit;
31.  
32.     ParticleSystem gunParticles;
33.     LineRenderer gunLine;
34.     AudioSource gunAudio;
35.     Light gunLight;
36.  
37.  
38.     // Use this for initialization
39.     void Start () {
40.         agent = GetComponent <NavMeshAgent> ();
41.         health = GetComponent <EnemyHealth> ();
42.      
43.         gunParticles = gunEnd.GetComponent <ParticleSystem> ();
44.         gunLine = gunEnd.GetComponent <LineRenderer> ();
45.         gunAudio = gunEnd.GetComponent <AudioSource> ();
46.         gunLight = gunEnd.GetComponent <Light> ();
47.     }
48.  
49.     // Update is called once per frame
50.     void Update () {
51.         gunLine.useWorldSpace = true;
52.      
53.         if (health.currentHealth > 0) {
54.          
55.             if (Time.timeScale > 0) {
56.              
57.                 if (target.GetComponent <PlayerHealth> ().currentHealth > 0) {
58.                  
59.                     distance = Vector3.Distance (transform.position, target.position);
60.                  
61.                     if (distance < attackDistance) {
62.                         agent.Stop ();
63.                         Attack();
64.                     } else {
65.                         agent.SetDestination (target.position);
66.                         attackTimer = 0;
67.                     }
68.                  
69.                 }
70.              
71.             }
72.          
73.         } else {
74.             agent.enabled = false;
75.             DisableEffects();
76.         }
77.     }
78.  
79.     void Attack() {
80.         attackTimer += Time.deltaTime;
81.      
82.         if (attackTimer >= attackDelay)
83.             Shoot();
84.      
85.         if (attackTimer >= effectsDisplayTime)
86.             DisableEffects ();
87.     }
88.  
89.     void DisableEffects() {
90.         gunParticles.Stop ();
91.      
92.         gunLine.enabled = false;
93.         gunLight.enabled = false;
94.     }
95.  
96.     void Shoot() {
97.         attackTimer = 0;
98.      
99.         gunAudio.Play ();
100.      
101.         gunLight.enabled = true;
102.      
103.         gunParticles.Stop ();
104.         gunParticles.Play ();
105.      
106.         gunLine.enabled = true;
107.         gunLine.SetPosition (0, gunEnd.position);
108.      
109.         shootRay.origin = gunEnd.position;
110.         shootRay.direction = new Vector3(-gunEnd.forward.x, -gunEnd.forward.y - 0.1f, -gunEnd.forward.z); //-gunEnd.forward
111.      
112.         if (Physics.Raycast (shootRay, out shootHit, shootRange)) {
113.             PlayerHealth playerHealth = shootHit.collider.GetComponent <PlayerHealth> ();
114.          
115.             if (playerHealth != null)
116.                 playerHealth.TakeDamage (attackDamage);
117.          
118.             gunLine.SetPosition (1, shootHit.point);
119.         } else {
120.             gunLine.SetPosition (1, shootRay.origin + shootRay.direction * shootRange);
121.         }
122.     }
123.  
124. }
125.  

Spoiler: Vector3.MoveTowards() Script

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SecondaryEnemyCraftAI : MonoBehaviour {
5.  
6.     public Transform target;
7.  
8.     public float attackDistance = 20.0f;
9.  
10.     public float attackDelay = 0.75f;
11.  
12.     public float effectsDisplayTime = 0.2f;
13.  
14.     public Transform gunEnd;
15.  
16.     public float shootRange = 20f;
17.  
18.     public int attackDamage = 10;
19.  
20.     public float speed = 10;
21.  
22.  
23.     float attackTimer;
24.  
25.     float step;
26.  
27.     float distance;
28.  
29.     EnemyHealth health;
30.  
31.     Ray shootRay;
32.     RaycastHit shootHit;
33.  
34.     ParticleSystem gunParticles;
35.     LineRenderer gunLine;
36.     AudioSource gunAudio;
37.     Light gunLight;
38.  
39.  
40.     // Use this for initialization
41.     void Start () {
42.         health = GetComponent <EnemyHealth> ();
43.      
44.         gunParticles = gunEnd.GetComponent <ParticleSystem> ();
45.         gunLine = gunEnd.GetComponent <LineRenderer> ();
46.         gunAudio = gunEnd.GetComponent <AudioSource> ();
47.         gunLight = gunEnd.GetComponent <Light> ();
48.     }
49.  
50.     // Update is called once per frame
51.     void Update () {
52.         step = speed * Time.deltaTime;
53.  
54.         gunLine.useWorldSpace = true;
55.      
56.         if (health.currentHealth > 0) {
57.          
58.             if (Time.timeScale > 0) {
59.              
60.                 if (target.GetComponent <PlayerHealth> ().currentHealth > 0) {
61.                  
62.                     distance = Vector3.Distance (transform.position, target.position);
63.                  
64.                     if (distance < attackDistance) {
65.                         Attack();
66.                     } else {
67.                         attackTimer = 0;
68.  
69.                         Vector3.MoveTowards (transform.position, target.position, step);
70.                     }
71.                  
72.                 }
73.              
74.             }
75.          
76.         } else {
77.             DisableEffects();
78.         }
79.     }
80.  
81.     void Attack() {
82.         attackTimer += Time.deltaTime;
83.      
84.         if (attackTimer >= attackDelay)
85.             Shoot();
86.      
87.         if (attackTimer >= effectsDisplayTime)
88.             DisableEffects ();
89.     }
90.  
91.     void DisableEffects() {
92.         gunParticles.Stop ();
93.      
94.         gunLine.enabled = false;
95.         gunLight.enabled = false;
96.     }
97.  
98.     void Shoot() {
99.         attackTimer = 0;
100.      
101.         gunAudio.Play ();
102.      
103.         gunLight.enabled = true;
104.      
105.         gunParticles.Stop ();
106.         gunParticles.Play ();
107.      
108.         gunLine.enabled = true;
109.         gunLine.SetPosition (0, gunEnd.position);
110.      
111.         shootRay.origin = gunEnd.position;
112.         shootRay.direction = new Vector3(-gunEnd.forward.x, -gunEnd.forward.y - 0.1f, -gunEnd.forward.z); //-gunEnd.forward
113.      
114.         if (Physics.Raycast (shootRay, out shootHit, shootRange)) {
115.             PlayerHealth playerHealth = shootHit.collider.GetComponent <PlayerHealth> ();
116.          
117.             if (playerHealth != null)
118.                 playerHealth.TakeDamage (attackDamage);
119.          
120.             gunLine.SetPosition (1, shootHit.point);
121.         } else {
122.             gunLine.SetPosition (1, shootRay.origin + shootRay.direction * shootRange);
123.         }
124.     }
125.  
126. }
127.  

Answers for both would be appreciated!