JetBlue and Emirates announced today earning rates for flights on each others' metal starting on July 1. Discounted fares earn less (no surprise there) but there are options. For earning Skywards points on B6 metal here's the chart: There is also a double points promo for travel through September 30, purchased today or later. Registration is required. More details on the new Emirates/JetBlue partnership here and here.
Depends on where you otherwise have points stocked up. There's rarely one "better" answer across the board. If you collect points on B6 normally anyways and have a one-off trip on EK then pushing those points to B6 probably makes more sense. If you've got an AS account that you normally use that would likely be better. And that's before considering the earning rates.
