update ko lang dito, apparently (in my case, I've tested) totally separate allocation pala ng bandwidth/speed yung UL/DL, either that or default na priority ang DL.. yung max speed ko na 230kbps sa PLDT MyDSL is not affected even if may unlimited na upload speed..
dati affected sya, but it seems the newer protocol is to strictly enforce speeds, kung ang total speed mo dapat sa DL ay 250kbps, ang alloc mo for DL ay 80%, and UL is 20%, then you can never use the 100% for DL alone kahit ioff mo yung UL.
and some more technicalities, better upload rates from your end == better download speed from peers, simply because inaadjust ng P2P yung priority ng parts to better seeders and ginagauge nila yung capacity nung connection mo both ways.
TL;DR - Use unlimited upload/seeding speed, it won't affect download, gaganda pa nga speed.