I have or had most of the 50's on the market. Most fly well. Any of the name brand 50's will be just fine for someone at the hovering and sport (pattern) flying stage. Once you get to the full 3D level, you need to select a heli that suits your style.
Out of the 50's in my fleet, my SDX gets the most air time. It has a completely adjustable head design which allows it to go from ultra stable for the beginner to lightning quick for the pop n lock crowd. It's also relatively cheap to buy and own. Nothing wears out quickly and it survives crashes with minimal damage.
Can't say the same for the T-rex, Velocity and ElyQ Vision. They all fly well, but you will be buying many replacement parts as they break often and wear out quickly. The Velocity and Vision can both outfly the T-rex IMO. However, the Velocity is fairly expensive to buy, but parts are very reasonable. The Vision costs less to buy, but some modifications are needed to make it strong enough and eliminate design problems with the head. The T-rex is pretty boring unless the HS is turned up to 2200 and higher. I suppose the FBL setup is the best way to go for the T-Rex now.
Vibe is robust and it shows in the extra poundage. Not the 3D beast in my fleet, but it has a very solid and reassuring quality. You can fly it for years without anything wearing out. You can also do this with a Raptor Titan SE for a lot less money.
If you go with the Vibe there are things you can do to make it lighter and centralize the mass to make it more capable for hard 3D. The big block engines gave this model a new lease on life.
If I was in the market for a new 50 size ship, and money was not too important, I would get a Synergy N5 or MA Fury 55 for a nitro bird and/or the Logo 600 for electric.
Don't know if any of this helped the OP or not. It's just my view on the current crop of 50 class machines. Good luck in your choice.