an Align 550 3GX is a good heli to start 3D, it has a few good points other heli's don't , first it's size isn't what you'd think, it's much more 600 than 500, you would think it would be in the middle of a 500-600 but it's not. bigger is better in so many ways.
The battery is one expense where a 550 is better than a 600, to get a 600 to a good 3D standard you need 12S battery or two 6S battery's, a 550 does the same job with one 6S battery, I like to have at lest 6 flights when I go flying, that's 6 battery's for the 550 or £360 to me compared to £720 for a 600 and remember your battery's don't last for ever,
Align's are easy to get parts for and upgrades,
price no object then I'd have a Corbin 700 please, but at that price you could have 5 align 550's, the thought of learning to do 3D with one is just wrong, one day I would like a cobin but not till I can fly a year with out a crash, it's just to much money and it's to nice to crash,
a 550 is just right, loads of power and full size,cheap to fix, the worst bit to replace is the blades, your find that no mater what heli you get,
after learning on a top specked 450 FB heli's the FBL 550 3GX was amazing, I wish I'd of moved up as soon as I learnt to hover, the price to build my 450's was the same as my align 550 3GX,
I wouldn't buy any cheaper,