Depends on what you want. One is a good Tessar clone & one is a direct copy of the 50/2 Sonnar.
The I-26, I think, was an intermediate design between the earlier Tessar clones and the final Industar-61 design. That lens, especially the L/D version, is generally considered quite good. If compact appeals, the Industar-22 collapsible 50/3.5 is a very nice lens.
That said, a good Jupiter 8 is probably the best investment you can make - cheap, fast enough for most purposes, & with a very classic "look". The key is a good one so buy from a known seller - I like Fedka.
Search the galleries & I think you'll see what you're looking for.
William