I have both ASG MK23 and TM MK23, I 'upgraded' the TM and it worked pretty poorly but this was obviously down to me not the gun, the gun was SUPER fecking fine from day one until touched it.
The ASG worked just as good (at cqb setting) until an issue where it was loading two bbs at once and no one could work out why and I was basically told its cheap so not worth paying a tech to sort. I agreed.
Now I have 2, both of which dont work properly (have been saying for over a year that I will sort the TM though

)
If you are going to chuck new stuff into it, and play around with it then I would grab an ASG personally!!