My personal experience is that the J3 is a slightly better overall performer than the J8, but not by much. Given that FSU lenses are prone to wide swings in quality, any two examples could validate or disprove that assertion. Of course the J3 is f/1.5 vs the f/2 of the J8, so it's worth the investment if speed is important to you.
The Helios-103 is a very good lens. At f/1.8, it's faster than the J8, but slightly slower than the J3. It's optical formula is different from the Jupiters, so its images have a different feel. Personally I like it -- very sharp and more "modern". Considering the price, there's absolutely no excuse not to have a Helios.
If cost is a serious factor, and if the extra half stop isn't essential, I'd recommend buying the Helios.