Size-wise, the Soul of Chogokin and Sega Real Models are sort of similar, with the Chogokins probably being a bit bigger - don't own one of either series, but the Chogokins are rather large, going off of video reviews, I'd estimate that a Chogokin Eva is about the size of the Sega Zeruel.
Quality and accessory-wise, the Chogokins win by a long shot. Not only do they have die-cast parts and an overall superb paintjob, the Sega models are also rather old and the technology at the time was very limited, so I wouldn't expect too much out of them. Also, looking at images of the packages, they seem to be coming with about as much stuff as the Chogokins, but in significantly lower detail.
IF you have two at a similar price, go for the Chogokins.
Why don't you save the Princess next time instead of being such a baby? She would love it and maybe you could get a sweet kiss. ~ Joseki
Your point of view is horny, and biased. ~ glitz2hard
What about titty-ten? ~ Reichu
The movies function on their own terms. If people can't accept them on those terms, and keep expecting them to be NGE, then they probably should have realized a while ago that they weren't going to have a good time. ~ Words of wisdom courtesy of Reichu