I have to stress that ive not used my 3600 30C packs in my CAT. However, i did use both my 4900 25C and 3600 30C in my B4FT.
The 3600 felt more punchy but i may well be wrong.
I also had two 3200 20C lipos. I can tell you for certain that a 30C 3600 felt a world more punchy than a 20C 3200 in my 10.5 Tourer.
Northy always beats me at Worksop
so go for the 4900
Just to confuse you further !