Right i used to own a T500RS with the additional shifter, and it is by far the best wheel ive used out of the G25 & G27, the fact you have so much control over feedback and settings in general makes a beautiful playing experience with Assetto Corsa or NFS Shift.
Now ive used the G29, and its actually a really really really well made wheel, its comfortable and Logitech really stepped up the game with this, feedback is slightly jerky/notchy im assuming it isnt belt driven. But other than that its hard to fault
What i would suggest is you go for the T500RS or the G29, i would say to leave the G27 alone as i've read people not being able to get it to work correctly with Windows 10 not sure if thats been fixed yet but few months ago this was the case, and as always it comes down to how much you want to spend, and how much you intend to use it, also the T500 allows you to changed wheels its self based on the type of game, i know they sell a porsche wheel and a formula one wheel. Also you can do some very nice mods to the pedals to simulate very very very realistic feel most common being the 'Brake Mod' with replacement of bushes and springs give one hell of a pedal feel, also the pedal orinitaion can be switched around so you can find what's more conformable i personally liked the high mounted layout as you can really use better driving techniques such a heel toe etc
Now if you really wanna get stuck in look at the Fanatec range of stuff i cant comment too much on these as i've not had the pleasure of using any of there equipment, but i haven't read a single bad thing anywhere.
