I have had both and was able to compare them directly.
I had a Clearaudio Concept but with the Verify arm for about 7 years. It's a nice looking deck and sounds good too. However mine required the platter bearing to cleaned re-oiled quite frequently (factory supplied oil) or it would gradually lose speed.
I now have the Technics SL1200GR and for me it's a much better TT.
It has a noticeably blacker background, more dynamic and overall sounds better.
Removal headshell making it easy to swap cartridges.
Zero speed issues and the platter starts and stops way faster.
Antiskate and VTF are adjustable via dials on top of the deck. On the Concept to change VTF you have to get underneath the table.
Th only thing that I don't like are the blue LED lights. They are very bright when the room is darkened. I remedied that by covering the lights with white electrical tape cut to size so it's not very noticeable.
Hope that helps!