I was under the impression the J-10 used a version of the RD-30 (?) or something.
still with 125Kn is still less than the 140+ of the F-16 versions.
and I wouldn't trust the chinese engine ratings up to the point they have been exported to another country and verified.
I think your question can be easily answered.
I don't knock the J-10(a or b) down, I don't much care to be honest, to me this is a hobby nowdays.
all I am saying is, that on one hand we have a fighter series with lineage. On the other hand we have a plane which is out for only a few years, and then it is being redesigned to a new version.
Western aviation history (more open) has shown that redesigns usually address shortcomings in the original design apparent during use.
so in my eyes, until data surfaces that says otherwise, the J-10B is a fix on the J-10A.
as far as the DSI goes, I mentioned before, the chinese figured out hot to calculate the DSI parameters and apply it to everything these days.
In my eyes it is a weight saving measure and nothing more.
as far as Pak. trying to line up to get J-10s.. well ..politics, don't think there is anything else behind that.