Need some help choosing batteries

[Rcaddict]

You guys have inspired me to go ahead with a conversion for an MBX-5. I've got Mike building a motor mount and I am going with a Mamba Max ESC w/ UBEC and a Neu 1512 2.5d motor with a 14/46 gear ratio. I want to run 4s Lipos and can't decide between 6000's or 8000's. I know glassdoctor has been having a lot of success with the Maxamps 2s6000 packs and I'm inclined to go with them because of the lighter weight. However, Mike recommends the 2s8000 packs for less stress on the batteries and longer run times. What I'm wondering is will the extra 6 oz's for 8000's turn the MBX5 into a lead sled or will that put it at the same weight as a nitro buggy?