The op started this thread in prehistoric times, we e.g. have the new asph/apo cron to consider as well.

But the choice is unlimited in 5cm lenses it should include the Cosina f/2.5 and /1.5 lenses, as well as Nikon LTM, Canon LTM and many other manufacturers.

In 40mm the Leica CL, Minolta CLE, and Cosina are all you have.

Unless you shoot wide open and tripod mounted you wont detect much difference in MTF.

If you like the single coated signature or multi coated signature you have choices in 4cm, and 5c,m, e.g. many of the Cosina 4cm are in SC

If you want small and light the CL, CLE, 4cm and Cosina /2.5 5cm and post '94 Elmar 5cm are all small and light, the Cosina /1.4 4cm is quite large amd heavy in comparison. The post 94 5cm Elmar is really good for MTF and high contrast

But the most critical thing if you do fast shooting is the ergonimics of the lens and your hand size, try before you buy, all the optical performance of the apo/asph is lost of you dont push the shutter release in time.