Do German or Japanese knives hold their edge longer?
The reason you're seeing conflicting opinions is because there are a number of factors (including steel composition, grind angle, grind profile, and usage) that contribute to a knife's edge-holding ability.

German/European knives are made of a softer steel than Japenese knives - they need sharpening more often but are easier to sharpen because of the softness.  Since the steel in Japanese harder, it needs to be sharpened less often.

The other factor is the angle of the edge - the German/European angle is flatter than the Japanese knives.  This means the German knives take 'abuse' better on the edge and requires less sharpening because of that.  You can see below that there are two different angles:



As far as which requires sharpening less, I'd say it depends on how general purpose your knife is going to be.  If its going to be going through bone and all sorts of things, the German edge will probably stay a bit better and the softer steel will re-hone better.  If you're mainly cutting veggies, breads, cheeses, and other soft items - the Japanese knife will last longer because the difference of edge doesn't matter as much as the steel here.