Time.deltaTime or Time.fixedDeltaTime for animated textures, such as a movie without sound (sequenced textures)

What is the best choice? with Time.deltaTime I sometimes get some "timeskips" when adding the value to a variable, in the Update():

 currentMS += Time.deltaTime * 1000;

The init value is 0 (int), but when adding the currentMS = Time.deltaTime * 1000 (milliseconds), it sometimes skips and adds a high number, it can best be descriped as similar to a frameskip or a fps drop. Can I use FixedUpdate() with Time.fixedDeltaTime instead?

The code is based on images (frames) extracted from a movie file. The frames are then inserted into an array. And the code switches frames based on fpms (frames per millisecond).

 m = frames per millisecond
 f = frames per second
 
 m =(1/f)*1000

My current code is here:

 using UnityEngine;
 using System.Collections;
 
 [System.Serializable]
 public class SVideo : MonoBehaviour {
     
     public Texture2D[] frames;
     public bool isPlaying = false;
     public int fps = 1;
     
     private int ms = 1000;    
     private float currentMS = 0f;
     private int i = 0;
     
     // Use this for initialization
     void Start () {
         ms = (int) ((1f / (float) fps) * 1000f);
         Debug.Log("FP-MS: " + ms);
     }
     
     // Update is called once per frame
     void Update () {
         if (isPlaying) {
             currentMS += Time.deltaTime * 1000;
             Debug.Log("Current MS: " + currentMS);
             
             if (currentMS >= ms) {
                 currentMS = 0f;
                 
                 if (i >= frames.Length-1) {
                     i = 0;
                 }
                 
                 this.renderer.material.mainTexture =(Texture) frames[i];
                 i++;
             }
         }
     }
     
     void OnDrawGizmos() {
         Gizmos.DrawIcon(this.transform.position, "SVideo.png", true);
     }
     
     public void Play() {
         isPlaying = true;
         audio.Play();
     }
 }