From the ones you posted.. It depends, first of all the earlier ones have the malus of not being fully developed like the ones choosed in the end (that tall Chopper has not many details and pretty much that is the same even for the others) yet with them we can wonder how the characters would have been like and think maybe something cooler than the ones used could have been born (talking about the robo arm Nami with a giant axe).
Anyway:
Chopper: pre skip, early concept, kawaji mascotte post time skip.
The hat and ability to change forms is better than a tall human-reindeer swordsman (?), I don't see much potential from that sketch compared to what Chopper is (was), yet post time skip he just got some new forms but was pushed in the background and his main role is that of a kawaji mascotte, pre timeskip Chopper was better.
Nami: early concept. We have seen pre skip Nami who become fanservice Nami, anyway her looks and perks were just that of your usual beautiful female lead character. If you instead gave her a robo arm and a giant axe as a weapon.. That would have been interesting, maybe it would have turned her in some sort of female Zoro or Yamato but maybe it would have been something new, cool and original.
Usopp: current Usopp. With him being some sort of old captain or Oda let him be the same character wise, or even more most likely, boastfull character yet afraid of everything just that he is an old captain (and better a youngster just like Luffy, otherwise we wouldn't have the Water7 Usopp story) or some sort of old dude/ even mentor in somethin maybe, maybe a character very similair to Brook.. Anyway from the looks it was just some sort of old pirate captain, a poor man version of Roger design, better the Usopp we have.
Sanji: better and way more original a cook who doesn't use his hands to fight so only leg style than a gunslinger even if now that I have seen Sanji I wouldn't mind to see Oda develop a real gunslinger strong fighter as one of the main characters, not something like Usopp of course, have as a one of the main characters somebody like Izo who managed to disarm even King, it would be cool to see that, even close range gunslinger vs other fighting styles, lot of possibilities. Yet all in all Sanji leg atyle is more original and most likely better.