I think primeGPU made a wrong business decision to offer this miner in exchange for XPM when it came out. He had the fastest miner in the beginning, it made sense to solo mine at the time. But a lot of people who had the right hardware, didn't have 65 or 35 XPM, so they used Claymore's miner instead. Then Claymore's miner became better, difficulty became greater, giving everybody little reason to switch and go solo. There should have been a 10% dev fee from the start, instead of 65-35-25XPM per license. PrimeGPU would have way more XPM now and so would the users of his miner.
fundamentally Claymore's miner updated faster, offered options to pool or solo mine.
Only primeGPU would know if it is better to charge a fee or use dev fee, as only he knows his users base.
From user's point of view, if you have > 2 GPUs of decent speed, it is better to pay 35 XPM since you should be able to ROI, even better if pool option was in in the first place (assuming w/o dev fee). However, solo mining is not that popular; most ppl prefer stable income and primeGPU does not have the means to collect % of earning from solo mining early on.. was until Claymore showed it was possible.