I owned an EX8 (before I ran it over with my van 😳 ), and with the insurance money I bought a Niner – not a Rumblefish but close enough.
The Niner allowed me to increase my downhill abilities in a huge way. I lose nothing on handling. The EX8 ascended much better – except on technical terrain where the larger hoops help get over over obstacles.
The main drawback of the 29er is in steep ascents – it takes about 30% more energy to climb.
Your choice really depends on a couple things: what kind of terrain do you typically ride? What is your riding style? What is the most important aspect of the ride?
Love those ‘tough’ choices!