If you're referring to the KJW "Cansoft" guns with clear lowers, the reason a TM is better is as follows:
TM is better than KJW.
It has nothing to do with the clear lowers. A Cansoft KJW is just as good as a regular all black KJW. They perform exactly the same, and the reviews only for the all black versions hold true to the clear versions.
That being said, TM guns in general have a much better review base: and from my own personal experience, are much easier guns to maintain and upgrade. Technically speaking, a lot of KJW guns are compatable with TM parts. This does NOT mean that they are as easy to upgrade with TM upgrades, because KJW may or may not have different levels of quality controls. TM has very high quality control, and thusly, upgrades made to work with TM guns take little to no adjustments to make work as advertised.
In my opinion, try to get a like new, or non upgraded TM HiCapa 5.1 or 4.3 with all the factory parts. They pop up quite often and are great little shooters.
Ár skal rísa, sá er annars vill
fé eða fjör hafa. Sjaldan liggjandi úlfur
lær um getur né sofandi maður sigur.