My personal experience:
I own a) A Garlando World Champion (bought new in 2007) b) Tornado grey marble (bought used in 2010) c) 2 Fireballs (bought new recently)
In terms of robustness I would have to say the best is FB, then Garlando then Tornado. Tornado has issues like men cracking around the head area, chipped bearings, chipped goals (mine has the first two but not chipped goals). Mind you, I think the Tornado is older than 2007 so maybe it's an age thing but I bought it in good condition so maybe it wasn't all that played on either. Been banging on Garlando for 6 years and absolutely no problems with it. Fireball is built like a friggin tank and I can't even envision having serious issues with it.
In terms of playability I would say FB and G are about neck and neck. G is a little more finicky because the men's feet are so small. So your actions need to be precise and sharp. Control on G takes time to develop. I've only played on FB for a couple of weeks and the transition to it is rather easy. Control is good but I find the rods just aren't as smooth as G so it will take time. T is good but the transition curve to it is just incredibily steep. It's a tough adjustment that many European players seem to have trouble with. I find T to be too bulky and not refined. But I'm sure T players will probably feel the same about G or FB.
If you're considering buying new then FB is, hands down, the best value for money IMO. If buying used then comparisons get a little tough to measure because it will be based on a table-by-table basis. Plus, as you mentioned FB is tough to find used.