In my novice opinion - the proofs (certainly the modern ones) hold a lot more visual appeal, but they don't have either the honest charm of the bullion coin or the close connection to the gold price. And I feel happy handling the bullion sovereigns whereas you wouldn't, shouldn't or couldn't with the modern proofs. I'd rather spend modern proof money on an older bullion coin such as a nice Victoria shield reverse, or perhaps a Guinea or fractional guinea. I've only got a few modern bullion sovereigns but I'd love to add a small handful of older ones at some point.