Warning, not a big builder here
The fighter approach will net you more combat feats, while the swashbuckler will give you more skillpoints. From a combat perspective fighter should be stronger.
(3 combat feats, which would also unlock weapon specialization, vs weapon finesse and grace +1). However, there will be some changes in a future patch:
epic prcs will come in the future, which are 10 additional levels for prcs with currently 10 levels, between 20 and 30. I think I read something about a change in the feat progression of the eldritch knight, too, maybe also in the bladesinger class? Not too sure though.
I'd say, approach it from a RP perspective: do you want to play the role of the bladesinger? From what I heard, the bladesinger is also not perceived as the most powerful class, more on the weaker side, but I think the fun in RP is more important.
"Bladesingers are elves who have blended art, swordplay, and arcane magic into a harmonious whole. In battle, a bladesinger’s lithe movements and subtle tactics seem beautiful, belying their deadly martial efficiency. Bladesingers have a treasured place in elf society, balancing the joys of art and magic with the skill of masterful fighting, and so bladesingers are well-respected by other elves. They usually serve as itinerant guardians and champions of the elf community at large rather than tying themselves to one particular settlement. "
