There's a major difference: Tai is looking for someone to settle down with; Sven is under no such delusion and is just out to keep his wick wet. (I grant that maybe this last statement is a wee bit of an overstatement, especially as Sven seems to be finally beginning to understand he might enjoy a long-term committed relationship. Maybe even with May. But that certainly describes his overt behavior to date.)
Tai also has issues about who she is sexually and her reaction to her own anatomy - moreso than many women I've known. Sven has none of these concerns.
So based on those differences, I must disagree.
Wait, did Tai have issues vis-a-vis her reaction to her own anatomy? I don't seem to recall that, but it's been a while since I re-read the whole comic so I'm kinda hoping somebody could point me to that.
Anyhow, I do agree that there appear to be some superficial similarities between Tai and Sven, enough at least to make it noteworthy that Dora chose to be in a relationship with her.
With regards to Tai always having looked for a long-term relationship, this is of course true, but we don't know what Tai used to be like. Given Sven's general development and trending towards that direction as well, it's not difficult to fathom that Tai was just a couple years ahead emotionally in that sense compared to Sven.
Anyway, Sven has been more of an asshole than Tai, for sure, but let's not forget that Tai's initial behavior in the comic was also not exactly great (nonconsensual cuddles with Faye, openly fantasizing/ogling Dora with Marten around, etc.).