Tough choice . MS have a decent product in J longhaul but the catering can be mixed. LOT have an ok J Class seat longhaul but not as good as MS. ( presuming you are getting the lieflat MS product ) If I had to choose personally I would take LOT .
When are you traveling? If in 2013 LO has a decent service and seat for IFE you will get a tablet. If you travel in March 2013 or beyond you will get the brand new experience with 787 from JFK to WAW.
As LAXIntl mentioned Lo currently does not service DOH from WAW, so you are most likely to fly WAW-DOH with QR.