I use PTR Retinol Fusion PM, and recently I've been using a sample of the Murad product. I agree that both are easy to apply, and if you can afford to use one on top of the other, it can't hurt.

If you can only afford one, I would pick the PTR. First of all, it can be used on your entire face, and the Murad can't. It takes about as much PTR to cover you whole face as it takes Murad to cover just a few wrinkles (since the PTR spreads so easily), so the PTR is cheaper. Finally, PTR almost certainly has more retinol than the Murad. The PTR has 1.5% retinol, which is one of the highest OTC formulations around. Murad won't release their concentration, which typically means that it isn't very high--if their formula was greater than 0.5% they would be advertising it.

The one feature in Murad's defense is that it contains hyaluronic acid which temporarily draws water to the area, plumping the skin and making wrinkles temporarily appear less deep.

Cheers!