It gets confusing at printing time, because I can never remember which camera or lens I used, and unless I make notes I can hardly tell after the fact. I don't print huge pictures, but usually 11x14 or 16x20 from those (mostly Tri-X, but some TMax, FP4, and HP5) negatives, and it's almost impossible for me to tell them apart, unless it was shot wide open (which I don't do much anymore). I use Leica enlarger and enlarging lens too, by the way.
They are all stellar performers, and work wonderfully in all sorts of situations. But if you really wonder what a Leica lens performs like, you should probably experience it for yourself. But for me it was kind of a light bulb moment that while you might be able to measure differences between a Summitar or a Summicron against a Pentax 50mm SMC, it will not really make a difference in the final print that is important. My joy of using the Leica has to do with how beautifully crafted they are, their precision, and how good they feel in the hand. Their silence is remarkable too. If I were you I'd get an M42 Pentax setup, and then start saving for a Leica if you really want to know what they're like.