Hi,
I have the AOP MEM and I like it. But my original lens was the Voight APO 90 before I upgraded. Both are fine lenses, you can't go wrong with either of them. Here are my thoughts.
I loved the voigt. The only 3 things that irked me were the 1 meter close focus limit, the large size, (you need to keep the hood on it so it becomes a longish lens) and the slow speed. But to be fair, I am unable to focus precisely even at 4 so 2.8 would be wasted on me anyway. While 1 meter close focus is standard it was always just too far away for me.
The good news is that it is the best value for money out there in leica 90s. I personally think it holds its own against the tele-elmarit and I would even have a tough time seeing a big difference when compared to the recent elmar 2.8. Yes, it's THAT good. The build quality is also excellent. No play in the aperture ring and smooth, consistent focusing. Mine accompanied me on a roughshod trip through Bangladesh, India and Nepal followed by a year of constant use in NYC and it never got a scratch on it. I can't recommend this lens enough. I am a little sad I sold it.
The APO MEM is 5 times the price, even without the adapter. It is better but not so much that it is worth the extra $$ in my opinion. Its main advantages for me are the small size when collapsed and the fact that it can get much, much closer than the voigt. The adapter is a pain to pull out and use but I find the normal close focus distance to be close enough for the detail shots I like to take.
The disadvantages are annoying though. I can't carry it uncollapsed in my bag, the cap won't go over the hood unless it is facing backwards. I am also suspicious of how strong the uncollapsed body is. I wouldn't want to keep it banging around like I did the voight. So I can never just pull it out and use it, I always have to go through the procedure of opening the thing up. Annoying. As I mentioned before, the adapter is such a pain to use it may as well not exist. And finally, compared to the voigt, it is ugly and attention grabbing. But the quality is excellent, really second to none.
Hope that helps.
