I have a TM Hi-Capa 5.1. Runs fine on HFC gas and has a nice clean kick with 285fps/.20g bb; on green gas, has a harder kick and ups the fps to 320fps/.20g, so it's still usable with indoor CQB rules. But I am aware that some (the Marui plastic) items will eventually wear/break and is in general not recommended to use green gas for long term (ab)use.
I looked/tried the KWA 1911/M226/KP45 and the H&K/Umarex USP Tactical and the WE 1911 MEU. I settled on the Marui Hi-Capa, as well, it's the Marui name. The USP/M226 were close seconds as these fit my hand well, not too heavy, fit a wide range of holsters; but there were limited accessory/upgrades available. Can't beat the Marui for the wide range of accessories and upgrades available.
Those items that can be prone to wear/tear/breakage are the loading nozzle, hammer mechanism, slide and outer barrel. The other potential weak point, is the gas flow valve on the TM mags; with green/propane these too will eventually break/leak. For that reason I bought a couple of the WE Hi-Capa mags ... one can buy high flow gas valves and R&R the Marui mags (use a valve tool). Seen the 51 round gas mag? Like wow for CQB!
Many update the slide and outer barrel with metal replacements; often with a tightbore barrel. I have a complete metal (aluminum) slide system - this has the advantage of slide off the old, slide on the new; the kit includes metal slide, front and rear sights, metal innner and outer barrels, spring guide, recoil spring, hopup unit and loading nozzle. In one kit I've updated the reliability items; can be had from $50 and up, shop around!
A GBB adds some realism and with the right upgrades, functionality too. And as a secondary for when your primary is down or you want to run n gun