Ive got through all sorts as use them for work.

IMHO

A Makita 14.3 or 18v is your best bet for ballance and quality

Travis Perkins are selling then for £103 at the mo with 3 batteries and charger.

Most important thing with cordless stuff is the batteries. THe tool will far out live the batteries. So dont be sucked into cheep deals and buy on quality and life expectancy

I had a bosch 24v for ages which was nice for stuff like decking, but what i found was that it was far too heavy for daily use. sounds funny but if your using it all day and have it swinging from you pouch whilst you climb on a roof then weight is important. as well as saving your wrists.

Only thing ive found with makita is the chucks get siezed so i try to only put hexagonal bits in rather than round bits like normall drill bits.

Bosch have just bouhgt out a new 18v combi, its supposed to have the power of a 24 with the lightness of a 12v. Never tried this one, but may be tempted as ive had 2 makita let me down on site now due to the clutch getting locked onto bits.