Format XD Card with Extended or leave as Fat

Which runs faster/better on IMac 17" Mid 2011 with Yosemite for the SD Cards Slot. I have recently acquired a SDXC 128 Gig card and it is formatted in FAT -- and I know I can reformat (somehow) to extended for Mac -- but which is faster/better, I know the Journeled Extended for Mac is more secure only working on Macs.