I personally enjoy the Kaplan
CATs more because:
1) I score higher on them. :D (Kaplan
- 760, Manhattan - 730)
2) I feel the Manhattan CATs unnecessarily push the difficulty of the Quant section higher.
3) Somehow the colours used in the Kaplan
CAT keep me calm and let me finish my exam 10 min earlier in each section. (Lame reason, I know! But whatever helps me during the CAT is precious to me
But the Manhattan CATs, on the the other hand, have their own benefits:
1) The exams are longer so make you better accustomed at working with a time crunch.
2) Are more friendly when you have a crappy net connection.
3) Have a solid verbal section that test out the grammar rules and don't let you rely on your "hearing" much.