Hughes built several 38 footers. The original was built in the mid to late 1960''s and was not a very good boat. The middle design (1969-1973)is the boat that I assume that you are referring to and the later boat called a Hughes-Northstar was a close cousin to the Catalina 38 and again would not be a boat that I would consider an offshore boat by any stretch of the imagination.
So I assume that you are referring to the late 60''s early 70''s S&S design. These are very interesting boats. The design was commissioned with S&S jointly by Hughes and Hinckley. Hughes built one version of the boat and Hinchley built their own version. Hughes built the molds and laminated the hulls, decks and misc. fiberglass parts for both boats.
i think that you are mistaken about there being several different designs. According to sailboatdata, all four different Hughes 38's are S&S design #1903. They vary only in their deck layout, cockpit design (size and tiller vs wheel) and interior. The hulls, ballast, rig (except for the traveler) and engine are all the same for all four incarnations of the Hughes 38. The differences in the displacement and draft can be explained by the initial design to the CCA rule as a racing boat and the later use as a cruising design, and its increase in weight.
Sailboats built by Hughes Boat Works by year on Sailboatdata.com
You are certainly right about them looking like IOR designs, in the reverse transom, fin keel/skeg rudder, masthead rig. Yet they also look like CCA designs, narrow, deep, with long overhangs. i consider them transitional designs between the CCA and IOR rules. Your take on their performance at sea is interesting, as several other owners have stated exactly the opposite. Fatty Goodlander has gone on record as stating that they are fine sea boats, altho he critiques them for other things - interior wood, mast step, hull/deck joint, chainplates, and general build quality during certain eras of the companies existance.
Several persons on the internet state that the Hinckley versions had a deck built by Hinckley. The Hinckley decks certainly were different than the Hughes versions. The Hinckley 38's sell for twice what the Hughes versions do. Either that reflects better maintenance, or better original equipment or better name recognition, or all three.