| I've used both. I started with humalog, after about a year had trouble with highs, wasn't lowering me at all it seemed. I switched to novolog (yes, on my own) and found that I got much better reaction to it when I was using Lantus. I phoned Aventis and asked them if there was anything to my thoughts... they explained because Humalog is "human insulin" it reacts differently with Lantus because it's not Human insulin, and they found in trials Novolog worked better with many others.
for ME:
Humalog - onset 30-45mins peaked at 2hrs gone by 3.5
Novolog - onset 15-20mins peaked at 1.5-2hrs gone by 4.5
have to learn to run your own trials on yourself. not every diabetic is the same. btw.. Novolog is MORE expensive then Humalog, but most places cost the same. have to shop around. but i've never seen Novolog for less then humalog | 
