All good points from billy.f

15k avios likely won't get very far on QR because most of their flights are long haul.

If the OP is based in UK and doesn't want to play the airline status game they might also wish to consider opening a BA account and transferring any avios earned on QR to that. 15k will get them a free short haul return ex-UK, there will more earning opportunities via online shopping etc, or worst case they can transfer the avios to Nectar to use elsewhere. Eg. I believe 15k will then buy c.£75 of shopping at Sainsburys