Maazel's late Mahler is extremely slow - a style that may be more appropriate for Bruckner than Mahler. He is, however, a master of powerful climaxes. If that works for you, then maybe give it a try. Personally, I don't like M7 to be slow in the second half. Movements 1 and 2? . . . yeah, OK - as long as they're done well, i.e. sans flabby rhythms. Another strike for me is that I'm not a fan of the modern day Philharmonia in Mahler, or much of anything else for that matter.
Of the major London orchestras, when it comes to Mahler, I like the LSO in a sort of lean 'racing car' kind of way, while the LPO probably still retains something of a heavier sound that's more appropriate for Austro/German music. I'm still not a fan of the metallic 'whang-y' sounding Paiste tam-tams used ubiquitously in the UK (Paiste uses stainless steel in the alloy).