According to canon, once you gain an horcrux you turn into an easily recognisable monster. Depending on the exact effects (which aren't detailed) it may be that you have no way to re-enter society and thus no third option between living as a total hermit or as a lord of terror.

So, if your three options are: (A) achieve immortality, spend eternity hiding from the world; (B) achieve immortality, try to take over the world; (C) live in comfort and respect for less than 200 years;

you could argue that A is better than B, but C is pretty clearly worse than A and B. Although it may be pointed out that there's little reason not to wait until you're, say, 150 or so before trying that Horcrux thing.

Of course, there's (D) get hold of a Philosopher's Stone and pull a Flamel by achieving society-approved immortality, but that might just be the single greatest plot hole in canon HP. Speaking of which, the Stone was mentioned in passing during one of the early chapters of MoR, albeit only for its alchemical powers, so I'm curious to see if/how Eliezer handles its existence as a life-prolonger.