Hello, I am currently facing the same decision myself after an allergic reaction to inflectra (infliximab). Entyvio is still very new, so of course there isn't a lot known about how successful it actually is, but, from what I am told, doctors are very fond of it.
I don't know how much you have been told, but it's a very clever medication that works directly on the white blood cells in the gut, but doesn't touch the white blood cells elsewhere in the body, meaning you don't get the systemic effects on the body that you do with humira etc. This doesn't mean there are no side effects, but they are generally considered less likely.
The downside to this is that it takes longer to work than the other biologics because it doesn't work on the white blood cells already attacking your gut, it just stops new ones, so you have to wait for the old ones to die before your gut can start healing. If you have crohns disease they will give you 14 weeks for it to start working before they decide it isn't for you.
Personally, I am going to give it a go provided i'm given the go ahead, as from my point of view I don't have anything to loose, I have tried all other medical treatments and am not allowed any of the TNFs due to my reaction, so entyvio is my last option before trial medications.
This is a very personal condition though, I guess it comes down to whether you feel its worth taking a chance on it. No one can tell you for sure it will help you, no treatment comes with a guarantee, but the only way to know is to try it.