I am in the market for a modern LTM lens for my Leica IIIg and I'm wondering if those of you with experience with the 40mm f/2.8 Heliar have compared it with the 50mm f/2.5 Color-Skopar. The Heliar can be bought new while the C-S can only be bought used, but setting availability/price aside, which do you prefer and why? Thanks all for these wonderful samples.