iMac 27 or rmbp 15??

i currently have a 2010 13inch macbook pro, it still seves me very well, but i want something new now.

i am at university and only really use my laptop for online browsing, word powerpoint etc and some geomapping (arcmap gis), i also like gaming (bf3, bf4 when it comes out).

i'd like to know whether it would be better to get a 27inch imac and keep the MBP, or get the 15inch rmbp, i really like the 13inch form factor so am going to miss that if i go for the imac but ohwell. obviously waiting for haswell refresh etc.