As others have said, this is a very personal choice and a lot depends on what surgeon you have, as the choice must be one that the surgeon is both experienced with and confident in.
The most durable valve is undoubtedly a mechanical one at this point, so generally someone of your age who has an additional life expectancy of more than 15-20 years is advised to go with the mechanical. However, there are many developments to produce a valve, either mechanical or tissue, that will both endure the rest of one's life and not require Coumadin. In other words, there are mechanical valves being developed that aim to no longer require lifelong Coumadin or other blood thinners, and there are tissue valves being developed that promise to endure longer than normal tissue valves, even the balance of one's lifetime and thus not requiring additional surgery.
I am 50 and just had AVR with root and part of my ascending aorta replaced as well 4 weeks ago. I opted for a new kind of homograft (human tissue valve) called the CryoValve-SG (bioengineered with SynerGraft technology) that has had all the donor's genetic cells flushed out of it leaving a genetically neutral collagen matrix. The intent is that this valve will not calcify like other tissue valves and, indeed, will enable the recipient's body to grow, repair, and otherwise maintain it as its own. They have successfully demonstrated this with implants in animals. With implants in humans, they have shown that it does not calcify like other tissue valves in the short-term and, with several of these valves implanted in humans that have been observed because the patient was 'reopened' for other reasons (e.g., coronary problems), they have verified that the recipient's body has indeed populated the valve with its own genetic cells and thus 'adopted' it as its own. (See studies presented at recent May cardiothoracic surgeons conference in San Diego.)
So far, so good for me. My body accepted this valve very favorably and my surgeons are very pleased with it. In a few years, they will be able to tell if it is calcifying or not, and, if so, at what rate. If it does not calcify in several years or at least does so at a significantly slower rate than a normal homograft valve, then they will consider that it is working as intended and then will expect that it will last the rest of my life. In any case, they expect it to endure at least as long as a normal homograft, that is, about 15-20 years.
If you don't mind Coumadin, opt for the mechanical. If Coumadin concerns you, as it seems to from your message, then you might consider alternatives such as the CryoValve, the Medtronic Mosaic valve, the bovine pericardial, the mitral valve mechanical being offered by the Cleveland Clinic that promises to avoid blood thinners, or other valves that are recently developed but without a sufficient track record to be sure they will perform as expected.
In my case, I figure, if it doesn't work, in 15-20 years they will have developed something that will. It's a chance that I decided to take knowing what is at risk.
So, get informed as much as you can, work out a plan you and your surgeon are comfortable with, and then go with it. You will have our prayers and support all the way. God Bless.