I'm a Makita 18 volt Li-Ion user and have been for 9 or 10 years: the DHP482 is/ I'm told, the replacement for the DHP456 (which I have) and whilst that is a nice little lightweight drill and is great for piloting holes, driving screws, drilling with a spade bit or running brad point twist bits up to 12mm or so it is limited when it comes to really heavy mortising because it will get bogged down with the larger diameter auger bits 16mm or above) that you tend to need. For that a DHP458 would be better - more torque, more power, metal gears, etc. The DHP481 is AFAIK really a brushless, even gutsier version of the DHP458 - I have a DHP481 and it's a bit of a beast, but boy is it heavy! It will also drill masonry (brick, concrete block) walls almost as fast as a low-end trade 110volt SDS but it will also pilot drill (4.5mm twist bit) through 10mm wall box section steel and run the 5.5mm Tek screws we use and can run hole saws up to 150mm with care and the long handle (a catch can really hurt). I'm just not sure that you'd ever need one. Heck, the only reason I need one is because I'm doing so much really heavy stuff on my current project that there really was no alternative. You really don't want to use either the 458 or the 481 for prolonged periods above your head or for extended periods of screwdriving where you need to support the tool, though, because the weight will hammer your arm.
I had Makita 12 volt stuff in trade use for quite a few years years (NiCd then NiMH) and I managed just fine with that; a colleague of mine now does all his new builds using 12 volt brushless Milwaukee kit - combi drill, SDS and impact driver. For such physically small kit they are really impressive and well worth a look IMHO. Bosch and deWalt also offer some impressive kit in 10.8 volt (which is effectively the same - the "12 volt" thing is marketing hype).
A word of caution about battery technology; Li-Ion batteries have a limited life. Regardless of how you use them they will lose 10 to 12% of their charge capacity every year and at 40 to 50% of original charge capacity (or 5 years) they can start to become a PIA to use, especially the lower amperage ones (2Ah, etc) which will hold effectively no charge, or at least none worth having. Worth bearing in mind when making a decision. Also worth bearing in mind that in future if you want to expand your battery tool kit to include tools such as jigsaws, circular saws, etc the choice of battery (make, range, amperage) may be a lot more significant unless you want to buy more than one battery range, or extra batteries. It was a major part in my decision to go Makita 18volt Li-Ion when I finally did upgrade from 12 volt NiMH
