I have say you would never notice the difference I've used LRP, Orion, Intellect, Demon and Track Power and I keep going back to the Intellect batteries and at 40ish quid you can't go wrong. I think I will be replacing them with the HPI plazma 95C shortly. You just need to look for a high C rating for more punch, 45-95C batteries give good punch.
What car are you thinking about? Only reason I ask is that some of the brushless speedo's are massive and you don't have much room to fit everything in the car. I'm running a LRP Sphere TC Competition in my Durango it's now 5-6 years old it's still going strong.
Here's cheap setup that's brca legal
http://www.ebay.co.uk/itm/Team-Wave-...ht_2726wt_1037
http://www.ebay.co.uk/itm/Intellect-...1#ht_500wt_923