I had two Magicool G2 and they are really good for the cost and will not let you down just flush rad as usual. Also consider the finishes you want... the nemesis will have better longer lasting paint job so take that into consideration this is white vs black but this is how nice nemesis finishes can be:
(White GTS) the indents on side give it a nice looking stance.
\
This is a Magicool G2 in action...its not really "slim" perse but it looks good and works well if you want to dump more money into other components. its just a black slab
After awhile on lower quality radiators paint can start to ripple and flake off if you abuse it too much, Ive had alphacool rads ripple really bad before but nothing like that from Magi or HWLabs yet.