My opinion is that there aren't radical differences between the two loyalty programs. And one thing to keep in mind... the programs change all the time.

Last summer I switched from Hilton to Marriott for all my travel after a very careful analysis, and lo and behold Marriott changed their program a few months later.

Same with switching airlines from US Air to Delta. Shortly after I switched, US Air reinstated all the benefits that they had taken away -- which was the reason I switched to begin with.

So I am now making my decisions based on this: Which hotel chain and airline offers me the most convenience.

I've decided to stick with Marriott because they have more properties to choose from in the cities where I tend to travel. And I'm sticking with Delta because they offer more flights to those cities and more direct flights.

If you make your decision based on quantity and quality of options, you'll be happier in the long run because the competitive nature of the marketplace tends to even out loyalty programs over time.