I think the real differences between a wooden rebate plane and shoulder planes are width of mouth (shoulder planes usually have a very fine mouth), and precision of finish. Shoulder planes are intended for precision trimming and fitting, specifically for the endgrain of tenon shoulders (but they are of great usefulness in other applications) so are not intended to take heavy cuts. Rebate planes are intended to take out quite large amounts of material, working predominantly with the grain, so are wider mouthed to handle heavy stock removal.
I think the older Record planes fetch good prices because they have a reputation for being accurately machined and having blades of good steel. I've never used an infill shoulder plane, so can't offer comparison, except to say that infills in good condition are generally highly regarded.
I can say from experience that Clifton shoulder planes are of excellent quality, as is the little Preston bullnose plane I've had for years. The Clifton 3-in-1 plane (3110 from memory) is handy because you can adjust mouth width with the shims provided, convert to bullnose configuration with the extra nose-piece, or use in chisel plane mode. It's one of my favourite planes for finer fitting work.