You’re wise to carefully consider deck-finishing options for two reasons. Besides the fact that cedar is a very expensive building material, it’s also true that most deck finishes don’t work as claimed.
Independent testing shows that a great many finishes can’t stand up to the moisture and ultraviolet rays of the sun. The two products you mentioned, however, do have excellent track records.
The only trouble is that dog of yours. I doubt any deck finishing product can resist those huge nails. Even if you left the deck bare, scratches would still appear. From the test results I’ve seen, I’d go with Cabot Decking Stain in your case. It doesn’t let wood grain show through (it looks like paint), but it’s as tough a deck staining coating as you’ll find.
When scratches do get out of hand, you don’t need to completely strip the deck and start over. Instead, lightly sand the surface with a 120-grit abrasive in a hand-held random orbit sander, and then apply a maintenance coat or two of the same product you put on initially.