All combination planes have problems...some are a little worse than others....
here's some points I can remember right now. Maybe not fact. Just an opinion.
Record 43 .....better than the carter and shimanco versions because its fence is double barred....that means you can lock the fence better. Since its important to have fence and skate parallel, you can lock one side of fence and flex slightly off it to bring the fence into parallel.....can't really do that with single bar fences. And a lot of these single bar versions don't run parallel, and flex in use....whats the point.
Record 44......similar to 43, but can take a deeper cut....uno, depthstop further from blade edge.
Nice plane for grooving edges though. or rebating a long edge......add a Large face to that strong looking fence....excellent stability of wide part of board.
Record 50's......The 43 and 44's ride on just a single skate. practically that means that they only really work well when the skate and fence are close together.........practically also that means you really can only use the smaller blades in most applications, unless you've got a deep fence off a deep reference edge.(which doesn't happen much)
The record 50.....since it has two skates can handle wider blades better. ie. Can keep the plane vertical more easily.
The problems I've faced with 50's though can be numerous. The tolerences they've allowed for are too fine in practice. Can make plane setting and cutting difficult or slow going. The blades should protude out the sides of the bed more (can fix that if you like)
another problem is the skates bevel to a point, unlike say that 44 or 43....which sometimes doesn't run as well on soft timbers. Cut into the timber a bit leaving little lines, and slow down the plane.
Stanley 45's..........Similar problems to 50's though a little different because they clamp the blade better I feel. But, because there a longer plane its more crucial that skates and fence are kept in parallel...and are straight etc.
The biggest problem I've found with the 45 is its size. Unweildly. Harder to keep it vertical....and support knob shouldn't be there.....cause supporting the plane from there worsens its use IMO. Handles too high too.
Stanley 55........same problems as the 45 with extras. Except it has excellent spurs.
As for blades.......Quite like the tungsten steel ones that come with 44's. Thats it.......don't get enough work between sharpenings with the other types I feel. Better off grinding your own blades from old files I reakon.