I would strongly disagree here. I think all Yamaha sets except possibly the DTX-500K are an upgrade from a TD-4. It is not a matter of settling for Yamaha.
My last kit was a Roland TD-4 and now I have a Yamaha DTX-535K. The Yamaha module sounds much better to my ears and the silicone snare feels much better than Roland's mesh heads, to me at least. As for the toms, rubber is fine. You don't do hours of buzz rolls on toms and Yamaha's rubber is soft and bouncy. If you are on a budget, the extra cost of the small single-zone silicone toms is not a bargain so the 535K is the steal of a deal with the Yamaha brand. (see my avatar pic)
Of course some drummers just prefer the super-bouncy mesh heads and they also prefer Roland's sounds. Not me, but every buyer should try playing and listening to both brands at the store before buying one or the other.
Both are excellent but some prefer R and others prefer Y.