^ Now that both services have upfront pricing, I've started checking Lyft and Uber for all trips and just go with whatever is cheapest. Oddly, I fly about twice a month out of LGA and I can't remember the last time Uber was NOT more expensive than Lyft going to LGA. Which is unfortunate, because I have to use that $15/month Amex credit.
Well as long as the difference is less than $15 you'll come out on top versus not using the credit at all.