Before I get rolling, I strongly suggest you go to the boutique and try on the styles you like to get a feel. I don't think you can make a fair judgment until you do so.
Now here's my story:
I had my heart set on a birkin, but there were none to be had in the size I wanted-- a 30. I need something lighter weight due to chronic, acute back issues. Not an SA but another tpfer steered me towards the Kelly. Turns out they had a 28 Kelly in orange and lord knows I adore orange; it was love at first sight. (So bought it new, obviously).
Fast forward to using it while shopping -- getting into and out of it is a pain in the arse. When I'm out shopping I end up leaving it unlatched because no sooner is it closed, I have to open it again to dump in something like the debit card or the paper receipt, or switch from sunglasses to glasses.
I now have a birkin just received it a few days ago -- bought from a tpf'er who was a very loving mommy. It hasn't been out on the shopping, test drive, yet, but we know you can leave it open a lot easier than the Kelly and it looks just fine.
In fairness, the Kelly is so dang classy, a tad dressier, imho than the birkin.
In hindsight, I failed to follow my own advice that I write so often on the Chanel side of the forum -- go with your heart, your first instinct and you won't go wrong.
I doubt I would have bought the Kelly that day had I been more experienced with Hermes. As far as buying new versus pre-loved, I'd go pre-loved again and again. I don't need that buying experience at the boutique. Heck, I buy scarves and other goodies there.
Take your time; don't be influenced by anyone but you.