There is at least 100+ different versions of the 'modern' reverso (post-1980), so finding the 'ultimate' is very much a question of personal taste. (not ot mention the also numerous vintage versions).
So, I guess the only reverso that can qualify to the term 'ultimate' is probably the reverso tryptique (most complicated reverso to date), but its price tag, plus the fact that it is actually too big to be worn keeps it 'ultimate' and not actually a likely real option.
Appart from that one, there is probably as many 'ultimate' reversos as can be.
For me, it would be a 1940's yellow gold dagger index central seconds, for others it could be the Art Deco or any of the complications series from the 1990's, and for some it might even be a squadra (argh!).
So, browse this place, and you 'ultimately' will find your own ultimate reverso, the one that matches your wishes (there are really many to choose from)




...IMO, the classic modern Reverso. It has everything a reverso should have, and nothing more: from its classic (i.e., non-XGT size), its guilloched dial (especially the non-harmonized version), to a genuine use for the reverso case (a second time zone). It may be considered entry-level, but I consider it to be the quintessential Reverso (akin to a simple, classic Patek Calatrava--say a 3919 or a 5119).
If by "ultimate" you mean the most impressive, then I'd have to say the new Reverso Gyro--one of the best looking pieces ever and a technological marvel.
John
Classic size, classic dial; rarity factor is nice; and perhaps most of all, it represented JLC's return to the reverso as the cornerstone of its line of watches; and in today's world of overpriced pieces, I think it still can be had for a relative bargain.
John