Without any experience of the higher priced spreads, I humbly offer my high praise for the Parker brush you're considering. It was my first brush after my return from the darkside of canned goo and I was and remain very impressed with it. I'm no badger expert, but the bristles seem way beyond what I associate with Pure grade (e.g., the quite okay Shea Moisture brush) and I would even place them above the Frank Shaving Finest that I also quite like. The closest I've got in my small (but growing alarmingly fast) arsenal is the Em's Place silvertip I acquired here on B/S/T. Both are big, soft knots that do better with soaps and creams than anything else in my collection.
I've got no experience with the Jagger brushes, but looking at the pix on your links, it sure seems that the Parker's knot is more like the higher priced EJ than the cheaper one.
Whatever you end up with, I hope you find it a nice change from your boar. I like to mix things up with my boars (Omega, Jaguar, CVS/VdH) and horsehair (Turkish no-name), but whenever I put the Parker or Em's to my face, it feels like coming home!
ralpho | The poorest guy in the human race/Can have a million dollar face - Burma-Shave