I have the S-works Stumpy from 2018 and ride around the Brighton area too, along with Wales and further afield when i can. It’s a 140/150mm version.
I’m using 27.5 wheels in it most of the the time, with larger volume (2.4WT) tyres and bike feels great. The Roval Carbons that came with it are not particularly light, so i wouldn’t buy the bike on the merit of the wheels. I only use the 29″ Roval wheels in the summer with fast rolling tyres on for longer days in the saddle.
For the shorter travel at 130/140mm i think the benefit of Pike chassis is not so important. For longer travel bikes, i reckon you’d notice the difference much more.
For the 1k difference i’d but the cheaper one, ride and upgrade back to Shimano (as i have done) when the bits wear out. It’s only the rear mech and shifter that will need changing, as the SRAM cassette will be fine with Shimano drivetrain. Spend the money you’ve saved on a better rear shock (a coil) and something towards some posh wheels maybe.
Its a fab bike for this area tho. Buy it.