In my eyes, Tekken 6 has a higher degree of variety a little ahead, because there are some features that do not exist in Street Fighter IV.
The adjustment can be alen 40 (!) Characters buy new clothes and weapons, equip them and so (also by changing the hairstyle and hair color, etc.) of each figure a completely own creation do (I have Lars after my "renovation "no longer detected). The possibilities are there countless, only expensive things and money are earned quickly only in campaign mode.
Which brings us to the next point: The Story Mode.
And yes: It is actually completely useless. Mission Mission kloppt you in Hack'n'Slay manner through small areas and has to comply with time limits. The actually relatively good frame story is by artificial stretching and pointless placed characters (you probably wanted all 40 process ...) botched.
But after all, Tekken 6 is a campaign. And as a distraction from the 1 vs. 1 This mode is always good.
Compared to Street Fighter IV the online mode not laggy, but he acts in a similar sterile and loveless implemented (but I do not think there has expected someone else). While each 2nd fight at SF I IV issues with strong Ruckelattacken remained something at Tekken 6 so far from completely; every fight has so far been smooth and presentable.
Even the bosses (Azazel) is not such a ***** like Seth. Although he is still unfair, but you can already plan his attacks and is really only Azazel tail attack really annoying. At least he teleports not always and takes a well not all the time across the stage ...
There is also a team battle mode in which more than one 8 vs. 8 battle either can be discharged against CPU or a friend. That makes a lot of fun and also offers variety. The mehrebenigen Stages (one crashes through houses, fragile soils, etc.) make a cooler impression.
Graphically, Tekken 6, however, no disclosure: pixelated edges and muddy ground textures rob the game the final touch. That was but in SF IV is not really better.
All in all, for me Tekken 6 in the lead because it offers me as a player much more variety and more figures are that are easy to navigate. In addition, the Panda and the kangaroo are of course also a plus. ;-)