the LSD is very detailed on its own. All of the tapes i've heard w/them have been through T+mod UA5s and V3s. no lack of detail at all.
but if you were farther away from the source, say in some OTS, then your 140s would be better. LD mics just dont work well from a distance...generaly speaking.
so no...I dont think you'd be taking a big step down. You'd get all the LD love from the LSD. go for it.
overall, my experience has been that SD mics are superior "all around" for ambient recording.
thats why you dont see the pros taping orchestra's w/LDs. always 4011's, 4006's and schempzies for the most part. YMMV, but you'll find out for sure with experience.