I use an upper/lower split, but I am a powerlifter so that makes the most sense. I do four days/week; Heavy bench, heavy SQ/DL, bench assistance, SQ/DL assistance. I've built way more size and strength using this type of training that using a more strict bodypart split for years.
Full body or upper/lower split
Pro's - better for overall size and strength
- more frequency of the main lifts (better for beginners)
Con's
- less able to focus on refining lagging areas (for advanced bodybuilders)
Body part splits
Pro's
- able to focus on lagging areas with more attention (for physique athletes)
Con's
- usually less frequency of training each area (using most splits)
- some compound movements don't fit into this scheme as well (are DL's a back or leg exercise or both?)(SQ and DL both hit many of the same muscles)
Ultimately I believe most will get the best results by focusing on increasing strength in the main lifts (SQ, DL, BP, military press) then training like a bodybuilder to hit the primary muscle involved in the main lifts (SQ then do something to get a pump in the quads, hamstrings, and low back; BP then do some rep work for the pecs and triceps, etc...).