I vote traditional every time. The scenario of your child being one of 3 or 4 in the same class is going to last only a few short years in the long run - whereas a 'unique' name leads to a whole lifetime of having to repeat yourself, spell it out loud, correct people when they pronounce or spell it wrong, or have to work twice as hard to 'prove' him/herself to people who are going to judge based on a name... things like job applications come to mind. We as a society may be moving forward but I can't help but feel that an older employer is going to take a resume from Madeline Smith more seriously than a Maddah-Lynn Smith, kwim?
I personally feel that a child is going to have an individual personality and be known for WHO they are, rather than what people call them, so I'd concentrate more on practicalities. My own name is technically 'traditional', but my parents did it in a way that is 'unique' and I have resented it for over 20 years - I don't think I'll ever get past it. The only saving grace is that 99% of people in my life now know me as Donna, not Donna-Lee as I was christened. It may be 'memorable', but it is actually quite humiliating when I bump into an old school friend and they shriek, 'OMG Donna-Leeeeee!' in front of everyone... yurgh! It's just Donna now, for the love of God! I just want to blend in and be normal! Donna's unusual enough in a generation of Melissa's, Carly's and Angela's!

Of course I only speak from my own personal experience, and there are lots more 'unique' names out there these days so chances are your LO won't be the only kid with a 'different' name in his/her class, but even so, I don't think a traditional name is a bad thing, even if a last-name initial has to be used for a couple of years, kwim? JMO, but I'd vote for traditional - saves a heck of a lot of frustration when LO grows up and can't get anybody to spell/say it right!