At the moment I'd say that neither YSMenu nor the official TTDS menu systems are fully adequate for my needs, or those of most people I know.
The official menus are, well, deficient - many people need to organise stuff by folders (by genre, app type, alphabetically, groups of one-screenfull to avoid scrolling, whatever...), and you just can't do that with the official menus. The more R4-like menu of YSMenu is a better fit to how I like to organise things.
By the same token, YSMenu has one serious defect in my opinion - Download Play doesn't work, or at least hasn't worked on anything I've tried with it using the Jan. 29 English version and the loader from 1.08 (and, of course, all the earlier versions of both that I've tried).
As a work-around I've re-named the official TTMENU.DAT to OfficialMenu.nds and stuck that in the root of the TF card. If I need to use Download Play, I launch the official menu from there. I'd much prefer it if I didn't have to, of course, but that's the way things are.
If download play isn't important to you, or you are prepared to jump through some hoops like starting the offical menu from inside YSMenu whenever you want to use download play, then TTDS + YSMenu is a great improvement on the offical menu. If/when Yasu gets Download Play working, I'll jump ship completely and start recommending the DSTT to friends who ask (although I still have serious reservations about the supplied TF reader's quality - and about a workable solution for a sealed cartridge if the TTDS starts showing the kind of problems that are solved with a shim when they occur in the R4). Until then, despite the present unobtainability, I'd have to recommend the R4 as more suitable for most people. YSMenu sucks far less than the official one, IMO and for my purposes, but until the Download Play issue is resolved there is no way to come close to the ease-of-use and ease-of-organisation and convenience of the R4 with the TTDS.