Only real argument for Nami v Laffite is that they are both Navigators but that alone is a weak argument imo given Laffite's rank and degree of prominence in the BB Pirates. Laffite being a Navigator doesn't mean he's weak, I mean his title of "Staff Officer" should speak for itself but if we have to really go into this, Scooper seems to have been Roger's Navigator, and he was the no. 3 strength wise.
Also the idea that Nami fights Laffite precisely bcoz he's one of the most prominent figures in the BB Pirates also doesn't make any sense as when as Nami ever really fought any of the antagonist's most prominent members?
Miss Double Finger was not more prominent than Mr2, neither was Khalifa more prominent than Jyabura, and Ulti sure as hell isn't more prominent than Queen.
That out of the way, some additional points on Laffite.
- In his initial designs (Gallery Memo) according to his Vivre card, apparently, Oda intended on having BB scout him directly from what looked to be WB's crew. So that alone should give u an idea on how Oda views Laffite. Sure Oda could have changed his mind after that but given his potrayal and all the info we know about him for now, I doubt that
- Laffite appears to possess a Flight Type Zoan which is said to be very rare (i.e iirc only 10 of them exist according to Oda).
Just to give a bit of perspective, in this arc alone, some characters with that category of fruit are King and Marco