As an owner of both G17's (Bell and WE), they both offer their own flava.
For instance the Bell is full trades, it comes vac sealed in a plastic bag with gun oil, and has a plastic carrying case (insert eye roll here). Like the WE it comes with a polymer body and metal slide, and most parts are compatible with the WE (some mods may be required). And as far as I can tell the hop up chamber unit looks like its TM. The gun shoots nice, hard, and accurate. Is able to accept WE/TM mags however the slide catch wont stop the slide on an empty WE mag (some mod is required on the mag itself-which I wasn't willing to do). It comes with a CO2 mag, and is compatible with gas and CO2. The mag is full trades as well, with a removable base plate to access the CO2 chamber, or to access gas fill valve (if you get the gas mag - it must be noted that I haven't had much luck with the gas mags and have opted for the CO2, and still tinkering). Final notes on the Bell is that it looks great shoots hard, but needs some tinkering for extended reliability i.e. new floating valve, hammer spring and recoil spring to get better gas efficiency, imo!
My WE is full metal slide with a polymer body, however the slide isn't a snug fit and thus has a wobble and noticeable noise. My WE is a Gen4, and that damn mag release is super sensitive causing the mag to fall out mid run......tactical fail..... it's not full trades but shoots nicely, and has great gas efficiency. If you can find a GEN3 I would recommend that for the money over the GEN4 (that mag release on the GEN4 is a buzz kill to say the least)
If you can get your hands on a HK3P GEN3 G17 (more expensive than a WE17 but cheaper than a TM!) then that would be ideal. Made by WE, but has full trades and metal slide. Can't speak for slide wobble, but it's something that I could live with as long as the gun shoots straight and reliably outta the box.