As a user of both ltm and M cameras, my own evaluations: the ltm Leicas are very pocketable and a little more convenient for much of my photography. On the other hand, the M cameras are generally more convenient and faster in everyday applications. Note, Canon ltm cameras offer combined vf-rf window, and also seemingly better build quality.
In a way, Leitz spurred the development of the SLR, with the appearance of the M3, which killed the market for all other rf cameras. So history testifies to its ease of use.
Prices on many Leica ltm and M lenses are reflective of Leica collector interest and have little relationship to practical value. However, ltm lenses were made by many: Minolta, Nikon, Canon, etc. Age does take its toll. Leitz lenses often have dendritic fungus, Canon’s often have haze, but clean lenses can be found. But for staters, only one camera and lense is needed, so use rather than difference in cost should be quiding factor.
Russian lenses are not an option. Look similar, but flange to film distance is different.