If I recall correctly, the Snells had an overall bigger soundstage w/ a wider sweet spot but the Proacs had better image specificity & depth. To be fare though, the room I had the Snells in before I switched to the Proac did not allow me to pull them away from the front wall sufficiently, only about 2 feet & & they probably would have liked a bit more. Also I had a Conrad Johnson Premier Four power amp that put out a real 100 watts / side w/ 4 EL 34 power tubes / side & w/ the low sensitivity of the Snells, they probably could have used more as I liked to play them loudly.
i once had the opportunity to borrow a friends amazing Jadis preamp which at the time was amongst the very best available. The combo of it , the CJ & the Proacs taught what real imaging was all about w/ space & air around & in between different instruments & voices in a beautiful unified whole. Not many systems that I’ve heard since could do this as well.