Et voilà. I go, I come back.
First up you will (naturally) have taken advantage of the copious amounts of info available online, readily accessible via the
Shrine to the Boat Anchor? A passing familiarity with the manuals of the most popular models can often make the decision for you. That's if you really mean it about only getting one...
Secondly, which are "good" is a horribly personal thing. It not only depends on what the individual user prefers in terms of weight, fiddliness etc, but also the state of the individual examples of models they may have tried. Viz: exposure to an unusable 050 with warped skates, wonky fence rods and so forth is liable to make Woodworker A vehemently dislike the 050, despite all Woodworker B's ringing endorsements.
My own personal nadir of awfulness in combination planes is an example of the intensely gizmotic Stanley #55. By sheer bad luck it turned out to have a full house of manufacturing cock-ups from which to choose and is still awaiting some work before I can make it useable. Had it been my first or second exposure to combination planes, I'd have likely given them up as a bad job and gone and bought another router instead, thus ending up on a quite different Slope. Certainly #55s as a whole would have been ranked as planes no sane galoot should wot of. And yet there are knowledgable, and indeed money-earning, woodworkers out there who wouldn't like to be without one.
Anyway, the 50S has introduced you to the wunnerful world of grooves, dadoes etc I believe, so the next logical step is upwards towards a full 50 or beyond and the joys of beads and so forth, rather than "down" to a 044 or 043. Right, putting aside the modern versions 'cos I can never remember the numbers, that leaves us with the most obvious and available Stanleys 50, 45 and 55, Record 050(A), 405 and the Lewin. I personally have a soft spot for the Lewin, but it's not to everyone's taste and it can be tricky to get one with all the parts and not too hammered, especially since some silly person put together a webpage on it. #-o
I hope it doesn't offend our 'Murrican membership, but generally speaking the Record examples are just that bit better in small but significant places, so I'd be inclined towards them. If you like the 50S, you may want to stick with that same sort of size and go with the Record 050. Personally (again) I prefer a little more weight and would go for the 405 - that'll give you sash, beads, ovolos, reeds (the latter ones if you can get hold of/make some) and is generally a pretty good all rounder IMO.
However, if you want to go off the gizmocity scale and tackle many and varied mouldings, the #55 (or Sargent #1085 if you happen to find one) is really your only viable option, but it's quite a lot to get your head round and they ain't cheap. There's also, as I've found, a lot that can go wrong with one, so I hesitate to actually
recommend it.
Having said all that, you could stay on the same lines as the 50S but go skewed and consider a #46. Excellent for cross grain work and many people love them - but oddly enough I've yet to be fully smitten by it.
Thus it is, as I say, rather a personal thing as to which are good. One of each is probably the safest way... :wink:
Cheers, Alf