blackajack: this is intended for you, to read through before pulling the trigger on something like ASR or HPSP. Others can read it if they're so inclined.
(disclosure: I'm currently in the process of applying for the National Guard ASR program. I looked into HPSP for about a year before ruling it out).
No one is going to be able to tell you the most financially sound options. There are just too many variables. You need to look at your situation and make some calculations. Some you can do now, some will be guesses.
Here's an example:
ASR will pay you about $51K/yr for three years (this is for me as married in California. Yours may be off by as much as $4k). In addition, you are eligible for a federal tuition grant of $4,500 each year. Total benefit to you would be about $166,500.
HPSP will pay you about $22,800/yr for four years plus cover your tuition. At your school, with tuition of $40K, this total benefit would be about $251,800.
So HPSP is the better deal. For the four years you are in medical school, anyway.
What happens after that? Well, it depends on the program:
ASR- You are a civilian free to take whatever residency program you are accepted to. For most residencies, you will fulfill your six year Guard commitment before you even finish, so you could functionally resign your commission (with two years in IRR) if you so wanted. If you decided to keep your commission, you would drill every month for a weekend plus two weeks a year. Current policy for mobilization is 90 days boots in sand (120 days max) every 18 months. Incidentally, I can't imagine us still being at that tempo when you come into practice in 7-10 years. We'd be bankrupt long before then. But there's no saying we won't find a new war by then.
HPSP- you will do a military internship. After that, whether you do a 2-4 year GMO tour or go straight through into residency depends on your service and your specialty. For non-competitive specialties, you might be able to go straight through. For pseudo-competitive specialties, it will be very service depenent (if you are EM-bound Army, you might have a 50/50 shot; if you are EM-bound Navy, you will go GMO first). After you finish your residency, you will practice as a military physician until your commitment is up. Depending on if you did a GMO tour and what residency you persued, this will be able to leave the service anywhere from 7-12 years after you graduated medical school.
Whether HPSP is more financially sound than ASR in the long term is going to largely depend on that last sentence. If you are in a decent paying specialty of any kind, ASR will be much more cost effective than HPSP. This is greatly compounded the longer you stay in the service. This is even more compounded if you are in a high paying specialty. There is a difference in pay between civilian an military practice. They are more comparable for low paying specialties (though civilian still has the prospect of going up faster than military); they are extremely pronounced for more higher paying specialties.
At the end of the day, HPSP will be more cost effective than ASR pretty much only if you are going to attend an expensive medical school, followed by a short military career in primary care.
DO NOT take either scholarship just for the money. Do it because you want to serve your country. After that, ask yourself, how do I want to serve my country, for how long, and how important is my ability to stop service when my needs or the needs of my family change?
Deciding between ASR and HPSP, I asked this and decided I liked the idea of ASR in which I would serve my country at time of war and my state in time of need. I like the idea that I'd be able to get the best medical training in the country that I was capable of (read: civilian residency) in any field I wanted, and keep my skills sharp in civilian practice. If my country felt it needed me in time of crisis, I'd be well suited to be able to contribute.
I ruled out HPSP because of the risk of a GMO tour (in which your skills atrophy as you wait to finish your training the way the medical community feels you need to), the risk of substandard training (some military residencies are on par with civilian ones, many, from what I've seen ,are not best-of-breed due), and the possibility of my skills being wasted in peacetime military stateside practice (volume is a problem in both surgical fields and emergency medicine).
If you dream of the career and lifestyle of a military officer, HPSP has a certain attraction. If you dream of serving your country when needed and being more-or-less a civilian when not, with the freedom to leave the service when you choose, ASR has great appeal. The two programs couldn't be more different.
Hope this helps...