Tendons (in my experience) tend to have a shorter life. The flesh colored ones will disintegrate in a few years even in dark storage. The black ones have held up better. Mechanical vs rubber is more personal preference. Rubber has a bit of give so often preferred in bumpier, rougher conditions. Rubber does have a finite life span, though, just longer than tendons.

Two bolt - cheaper in the long run if you have a lot of boards and like stuff rigged up and ready to go. Supposedly more robust in the surf (two bolts holding things down). Much less likely to slip or worse, completely come off your board. Can be easier to disconnect rig if your sail covers up the upper holes. Once you get mast foot placement dialed in, you don't have to mess with it each time you sail. Also, cheaper if you run a mix of euro and us bases (almost no one here). One bolts are better if you need to be near the edge of your mast track for whatever reason (like trimming for foil use in my case). One bolts are better if you are going minimal - one base covers all of your boards.

Old but probably fairly relevant: http://iwindsurf.com/forums/viewtopic.php?t=15166
Also, the Puffin: http://www.peconicpuffin.com/the_peconic_puffin/2008/05/two-bolts-or-no.html

My strong personal preference is for two bolt base with a tendon. I like the safety and convenience of the two bolt (as long you don't mind by buying a plate for each board). I like the feel of the tendon over mechanical, although I never tried rubber. Mechanical should be easier to attach and detach on the water. As far as durability, probably mechanical > tendon > rubber. I always test my tendon before sailing. I have had one break while testing, never on the water though (20+ years). I have two universal joints that I change about every 3-4 years.

One downfall of the two bolt though is that many windsurfing SUPs have a single bolt insert for their mast track. In that case you have to use a single bolt.

I like the mechanical two bolt best. It is more idiot proof (which is really important to me) because even if you don't tighten one bolt enough, the other one can keep the base in place. In fact, even if both are too lose, it is quite difficult for the mast to become detached from the board. Second, if you do actually do it right (and tighten all the bolts), it is stronger. Third, you can more easily attach the sail in the water, when launching or in the unlikely event it would come off in the water. I don't think you can bend a tendon enough to do that.

I would avoid he "Streamline" style tendons - they are cylindrical about 3" by .75" I think. They get brittle as they age (even in storage) and can break easily. I've managed to break one just by bending it with my hands.

I've had both an hourglass tendon and a "Streamline" tendon fail me on the water, but never a mechanical (yet).

On the foil board, I like single bolt for ease of adjustment and mechanical UJ for easier disconnect & reconnect... nice for adjusting downhaul on the water. I have a tendon on the Equipe because I think it transfers energy to the board more better. (Might be perception more than reality). On my shortboards, rubber joints for shock absorption and 2 bolt for security.

In the two bolt you do lose some of the travel in the mast base allowed by single bolt and, adjusting on the mast base position is easier with single bolt, so this is clearly preference issue more than one being a lot better than the others.

Black rubber

Just make sure to keep an eye on it every so often. Tendons are cheap. You may just want to get a new one every couple of years.