system
Given the following post, respond as if you're commenting on Reddit:
human
[Super Heroes] Is there any functional or practical difference between someone who can move/think up to twice as fast and someone who can slow time for everything except for them up to 50%?

The time dilation is not local; it is universal (except the user of the power) and cannot be contained.
gpt
Depends but usually the guy moving fast has secondary abilities like being able to withstand a larger amount of kinetic force and ignore environmental conditions such as friction to move. Additionally they tend to possess better reflexes and in the best cases be bullet timers to process the faster inputs which means they are able to "activate" their speed instinctively at higher speeds and react to danger more easily or always be sped up in which case everything is always slow to them.

Time stoppers usually have as weakness the need to know of a threat to activate their abilities and can thus be sneaked upon or sniped. They also lack secondary abilities and probably interact with the world as anyone would (a speedster may atomize things he touches or pack harder punches while a time stopper doesn't).