100 mm Prime for 50D, f2.8 Macro or f2?

Ah, life is tricky.

In the past months, I dived into the wonderful world of DSLR fotography with my 50D, Tamron 17-50, Canon 70-300, 4-5.6, IS USM, and 50mm 1.8II. I found myself using the two zooms most of the time, just because of the higher versality. Then again, I did a few nice close-up of cats and persons, so I am quite satiesfied with my choice. But I notice that I am missing a lens, that is tack sharp with a medium range, giving me that extra sharpness the two zooms can not deliver (and I think I have good copies). I think, a 100 mm on a crop camera would just fit my criteria. The lens would allow me to take pictures of no too large things or details with the desired detail.

Now the obvious choice is between the f2 or the 2.8 macro. I read that the 100mm Macro lens is very nice (and rather easy to use) for Macro work. Then again, the f2 lens will be sharper at 2.8 than the Macro lens. But will I really need the fastness, when I am not too much into portraits (I still have my 50mm, 1.8).

So, my tendency is towards the macro, since the lenses are similar in price and sharpness at apertures => f4.

The next question of course is the Sigma 105, Tamron 90 or Canon 100? I know the obvious differences like the price and the extending tube in the third party lenses.

Now I just learnt, Tamron will bring a 60mm f2 Macro. Soon, Then of course, I could replace my 50mm with the Tamron and would have Macro, and the world is wide open for the 100mm f2....
ah, life is so tricky and full of wunderful choices..
I appreciate any valuable comment or input for "my incredible dilemma" :-).

Thank you for your help.
Have a nice evening.

Christoph
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