It is definitely easier to accumulate points for Hilton, though they won't go as far as SPG points.
The Hilton Amex gives 6 HHonors Bonus Points for every eligible dollar you spend at Hilton Family hotels, and at grocery stores, drugstores, gas stations, wireless and home phone, internet, cable and satellite TB service providers. It gives 3 bonus points on all other purchases. The current offer is pretty good at 50,000 points.
http://www.flyertalk.com/forum/miles...-50k-easy.html
Hilton also has a Visa card with CitiBank. It gives 6 points at Hilton hotels, 3 points at supermarkets, drugstores, and gas stations, and 2 points on all other purchases. The current offer is decent at 40,000 points.
http://www.flyertalk.com/forum/hilto...us-points.html
You CAN get both cards together and you'd have 90,000 points to start with right off the bat. If you and your wife got both, you'd have 180,000 points to start with, plus whatever spend you put on the cards.
SPG only gives 1 point per dollar spent. SPG's points are definitely worth more, but their signup bonus is pretty poor currently. You only get 10,000 points with first purchase and you have to spend $15k to get to get 15k bonus points. So if you could spend $15k on the card, you'd have 40k points. 40k points could be stretched if you use their cash+points option.
All in all, SPG points have more value, but with the current sign-up bonuses, I think Hilton is the better option. You could easily have well over 200k points by the time you book your trip and if you utilize Hilton's cash+points option, you should have enough points for quite a few nights.
EDIT - As a Category 7 hotel, it would cost 50,000 points a night. If you use cash+points, it would cost 25,000 points plus $85 a night. If you had 200k points, you'd have 8 nights that would cost you $680 cash.