I've had both the TM and WE, both giving two very different experiences. Performance wise, there wasn't much of a difference to be fair and the WE feels a lot nicer due to the metal slide. The gas efficiency of the TM was better because of this, however. The trade marks on the TM were a nice touch though.
Now, their ends were different.
The TM malfunctioned due to the hammer breaking. Replacement TM hammers are impossible to find so I ended up just selling it after fitting it with a WE hammer assembly. The WE didn't actually break, which was great. I just ended up selling it because I no longer used it (I made some sort of pistol configuration from a rifle).
Also, the full auto feature of the 18 is not really practical. It's fun to have but fairly useless. Gas consumption is understandably heightened with full auto and the mags are emptied ridiculously quickly.
So yeah you're good with the TM as long as something like the hammer doesn't break, or some other impossible to find part. The WE is much easier and cheaper to source parts for. However, there are a lot of aftermarket parts which will fit the TM which won't fit the WE due to the slightly wider build of the WE. That may also cause holster issues.
Given the choice, I'd take the TM and put a nice metal slide on it. Maybe guarder or the Ace1Arms SAI style slide/barrel. But the WE is by no means a bad choice! Either way, I'd go for a G17 though.