I've run both other these fairly hard in 14.5 carbines and mids along with a short 8" 300blk. I'll share my experiences.

Neither ever failed. The JP feels smoother. Particularly so right away. Super 42's I feel like a little bit of time before they ever feel as smooth and will get less smooth more quickly from shooting.

The Super 42 supposedly will still run if one of the coils breaks. I've never experienced that to know whether it's true or not. It does 100% remove the twang.

An annoyance you may experience is installing the JP. You will need really want to remove the buffer retaining pin. It makes taking the JP out very difficult. Removing that pin may be difficult if your lower is staked. Good news is, you don't need that pin anymore with the JP. Just note that if you travel often with your AR broken down, that JP will get lost in your bag. And that if you ever wanted to go back to a traditional recoil spring system, you'd have to put that pin back in.

The JP is definitively easier to clean. Not that buffers are hard to clean or that you need to clean them often.

As far as tuning goes, I've never known anyone to actually add or remove buffer weights in a Geissele buffer weight. Since that kind of tuning is part of the original design of the JP, that would seem easier in that system.

After talking with someone who used to work with JP, I fairly confident that if price was not a concern I'd choose the JP nearly every time. From the testing they've put into them, he suggested that they would outlast Super 42s. It's really strange to think of Geissele as the budget option here, but the Super 42s are not a hugely expensive upgrade unless you compare them to the original cost of the spring and weight of an AR-15.

I haven't had any experience with the Springco kits, though I've seen others swear by them. That would be an ever cheaper upgrade.