Two equally skilled players (with specific regard to their dexterity) attempting identical actions on two different sticks will see a difference in their success rates, but it’s pretty small. Especially as a new player, if you attempt an action, and don’t see the result you want, it’s because you messed up. Any of the entry level sticks here (the VX, the EX2, and any of the SE family) are perfectly fine.
A slightly more lengthy explanation:
So, if there’s a result you want (throwing a fireball, let’s say), there exists some set of wrist motions that will activate the microswitches in the joystick in the order you want. When you make an attempt at throwing a fireball, if your wrist motions fall within the set of motions that the stick will count as a fireball, that’s a successful action. If it doesn’t, well, you should have moved your wrist differently. With practice, you can learn to end up in the successful set more often. This is true for sticks of all quality - If you didn’t get the move you wanted, there exists something you could have done to get the move you wanted, and you didn’t do it (assuming that your stick is not actually broken). The difference is that in higher quality sticks, the set of actions that count as “successful” tends to be larger. You have a higher margin of error, which is nice. But the delta between better and worse sticks is pretty minimal and can always be made up for with skill, so it’s not that big of a deal with regard to purchasing decisions, especially if you’re on a limited budget.
People with a more flexible budget and a penchant for obsession worry a lot about the difference between sticks not only with regard to the size of their “successful action set” but more with the spaces in which the successful action sets between two different sticks don’t overlap (i.e. In some cases Motion X will count as a fireball on Stick A but not Stick B, meanwhile, Motion Y will count on Stick B and not Stick A. Which stick do you want? Well, it depends on if you’re more likely to end up with Motion X or Motion Y), as well as some of the more subjective qualities of sticks. But that shit’s for crazies, and if you just want to punch some dudes, a VX will be just fine. I’ve been using one stock for the last couple weeks instead of my HRAP EX, just to get a feel for it, and I don’t really have a ton to complain about.