Humans have different stats - that human invoker will heal faster than the elf due to higher con. They can carry more due to higher str as well.
They can rank faster - a BIG plus for mages.
You can't be attacked as easily by those above you (wasn't there just a big whine thread about people getting beat up by pinnacles? We should be due for another next week...) and you can beat up on those much, much, much lower than you. I always suspected Poplin was a human because he wanted a wider range of bounties - not saying he didn't kill 50s, but he would have had a LOT more to choose from than say, Waojin. I played a human Syndicate thief for the same reason: More bounties = less boredom.
Humans get other bonuses too - read the helps.
General rule of thumb - the higher your xp penalty the more 'advantages' you have at lvl 50. Its the price you pay. Take a low xp penalty and rank faster with less 'advantages.' You knew what you were getting when you rolled the character.
Its not THAT hard to get to lvl 50, true. That doesn't mean its fait acommpli for a lot of people. Or that you will get there without me or a dozen other players multi-killing you in your final seven ranks if you are an elf paladin/drow dk.
Also, who REALLY cares if you are picking off lowbies all the time? Some meaningless post on a forum? I never hesitate to patrol ranking areas or kill low level characters of opposite align if that's what my character would do. Ignore will stop their whining (as will multikilling and looting) - and I back my game to stand up to their OOC friends who get called in (Duergar blm and gnome thief, I'm talking to YOU). Cabal IMMs never seem to mind as long as you're capable of discharging your cabal duties (mostly killing other lvl 50s of opposing cabals). Well, no IMM has ever had a go at me for it, and I've led a cabal or three in my time. Of course, my characters don't always have to run from other lvl 50s either 
L-A