The first one is one of the iterations of the G250HP while the second is a G250. The G250 had various purge cover designs, and either all metal splined adjustment knobs or plastic covered metal splined adjustment knobs, he grind used in the plastic case may have changed over the years, and the flow vane adjustment knob changed over the years, but they are all the same regulator internally and use the same basic balance chamber and poppet design (with minor variations in the balance chamber over the years). The current G250V is the re-incarnation of the G250 as the G250 was just plain better than the G250HP and a nice G250 was quite frankly starting to bring more on e-bay than you could get for a new G250HP.
Internally, your the G250 and G250HP are significantly different in terms of the plastic versus metal air barrel, the balance chamber and the adjustment knob and micro adjust feature on the G250HP. Given that the G250 lacks the micro adjust, the spring tolerances are much more precise on the G250 and the QA standards are necessarily higher as is the production cost of the G250's metal air barrel - but it is a much better second stage in my opinion as both a reg tech and cave diver.
