very well done. in response to Babahara, i'd say that 80% of the difference is in lighting and skin 'shine' effects. the actual shape of his face is almost spot on. 6 things are off with the character's face though, most of which are things out of the creator's hands:
1) Eye Shape [but to your credit, you did a very respectable job in sizing and positioning. actual shape would depend more on the positioning of the eyelids, which is very difficult to pefect in TS3]
2) Ear Shape [but you're not to blame there. it'd be very difficult if not impossible to match LaCroix's ears perfectly]
3) Lip Size and Shape [funnily enough, that's actually partly a mistake in graphical effects on VTMB's part, rather than your Sim impersonation. lip skin-sizing is off, as you can see in the first image with the VTMB LaCroix's face. however, IIRC [not quite sure, so don't hold me to this], there is a lip shape that somewhat resembles LaCroix's lips a bit more accurately. again, i'm not sure o this fact, as i haven't been in TS3 in over a week or so, and even longer since i was in the Sim Creator]
4) Hairstyle [i can give you a link to a more accurate, though by no means perfect hair replacement to better fit LaCroix. Oepu's Sims 2 conversion hair here:
http://www.modthesims.info/download.php?t=366004
5) Facial Hair: we have yet to acquire a brow that matches LaCroix's so this is by no means your fault. however the semi-clean shaved looking beard the Sim version has, doesn't match. i can see why you added it though. it does give the skin a more detailed look, so kudos to that.
6) Chin Width: it's ever so slightly thinner on the sim than the VTMB character, but again, i don't think that is really in your hands due to game restrictions.
all in all, a very well done Sim. i'm still thinking about whether or not to DL it though, as i'm somewhat afraid of the hack needed to add him accurately. will it effect already made Sims? and how will it effect me, as a character designer? will i need to do anything more than the normal work you do in the stock, unmodded game?
if the answers to those two questions convince me to get it, i'll DL this character and see if i can try and adress the issues to more accurately fit the VTMB version, though quite honestly, i don't think i'll be able to do a better job than what you've already done here.