As i see it the 50 is just a little bigger then the 30, the 60 looks awesome, but the 90 looks like the holy grail!!
There's not much more to explain
Ironically, the bigger ships will not cause you to "exceed your ability" since they are actually easier to fly. The only drawback to bigger is more expensive. Since your Uncle seems to be Donald Trump, log on and hit "Buy it NOW".
Tom