[Cliffradical]

That's a bit extreme.
Gas guns are high-maintenance. They are the girlfriend from a privileged background of airsoft guns. Even the best kept GBB pistol will eventually develop quirks and outright failures. Neglected GBBs will develop quirks and outright failures much faster and with more ferocity. All mags will develop leaks. These are guns where filling a mag with gas can kill a fill valve when done improperly. They don't like being too hot, and outright won't work if they're too cold.
I believe that someone's KWA 226 may have fallen apart in their hands, but 99.99% of those 0.01% of situations can be attributed to user error.


KSC/ KWA has much, much nicer externals and general feel. Their mags are easier to repair when they develop leaks. Their magazines, feed lips, and feeding system are arguably better. They have less in the way of aftermarket upgrades, but they work well enough that you probably don't need to go there anyway (depending on your expectations). You will want to purchase a replacement for nearly every part but the frame, because they can be infuriatingly hard to get at times.

KJWs have much more slop. That is both a detractor and a benefit. It's a detractor because while they don't have all of the lovely trademarks, nice sharp edges, and snappy clap, they tend to put up with more abuse. KJWs are not beauty pageant winners, nor gold medal triathletes, but they just work. You can neglect a stock KJW and it will continue to function beyond the limits of many guns of higher breeding.
Neglect will also ruin it like any other GBB, but if you're lazy (be honest), you'll get away with a bit more.

This all comes down to how you'll be using it.
If it will most often be your primary in a CQB arena AND you're really anal about maintaining your equipment, buy a TM and have a guntech upgrade it.

If you want a trophy wife that'll sit in a holster indoors and speak when spoken to, buy a stock TM.

If you want a gun that looks great and can be trusted to work how you want it to, and are willing to put in the effort to make sure it'll work when you need it to, buy a KSC/ KWA (KSC if you can get your hands on one).

If you want a piece of equipment which fills the function of being present and going BANG when your primary is down or you're otherwise bored, buy a KJW.
If after buying it you feel that you want more than a mere piece of equipment, you can buy a titted-up TM and they can share mags, though probably not holsters.

Edit: This post is late to the party and sounds grouchy. It's not grouchy, it's just weather-worn.