Well, Dr J, as you seem to wisely realize, one basic answer to your question is, "It depends." It's good that you clarify how you want to spend your points (on good vacations), but if you have the time and inclination you might want to consider what specific places (if you yet have any inkling) you might want to go to.

Another variable is whether you think you'd get status in a given program. HH Gold and Diamond gets you free breakfasts that otherwise could be very expensive; I believe that Platinum at SPG does the same for you. If you're not staying enough to gain status, but you spend a lot on credit cards, $30K per year on the Starwood Amex gets you SPG Gold, $40K per year on the Hilton Surpass Amex gets you HH Diamond, and I believe $20K (or is it $30K?) per year on that Surpass card gets you HH Gold. There's also another Hilton card (Citi Reserve) that I believe comes with Gold status, perhaps without a spending requirement.

In any event, back to picking programs and just to pick my own example: Overall, I think that SPG is the best program in terms of the perks, the ability to sometimes use the "points plus cash" option (whereby you can use relatively little $ and relatively few points for nice stays, which HH offers to only a very limited extent), and diversity of fine properties. So my wife and I will use our points to stay at three very good properties (Tambo del Inka, Hotel Paracas and Westin Lima) in Peru next September year, with even a fourth hotel in our sights (Palacio del Inka) if, as seems possible, it joins Starwood by then. BUT, overall, for beach/tropical vacations, we've found more Hiltons we like (based on FT and Tripadvisor reviews, as well as our own experiences) in Bali, the Maldives, French Polynesia, the Seychelles and Thailand (the Conrad Koh Samui). In certain places, such as FP, there may be a great St. Regis (part of Starwood), but IIRC the point redemption costs are astronomical or the option isn't available.

And yet another variation on this theme is that there are incredible Park Hyatts in Paris, Tokyo and Sydney, for example, if those are cities you'd like to visit. (Also, I've read very nice things about the Grand Hyatt in Tokyo and the Hyatt in Kyoto, FWIW.)

So this brings me back to my original point: You might want to consider exactly where you'd want to go, check out the hotel reviews and points required accordingly, also take into account whether you'd achieve status in a given program, and then decide where to deposit you points (splitting them between programs if appropriate) based on all that.

In any event, happy trails!