I haven't done the Discovery series, but I did travel with Gate 1 to SE Asia (Bangkok, Cambodia, Vietnam). I am a similarly situated traveler (solo, non-retired). I chose Gate 1 specifically because of the itinerary (was meeting a friend living in Northern Vietnam) and the reasonable cost. I essentially considered the tour my transportation/hotel infrastructure but was pleasantly surprised that tour guides were quite good. If there had been a Discovery option for what I needed, I would have picked it instead.
The one notable thing about the regular Gate 1 tours is they sometimes combine tours - for example, for my SE Asia tour, I was one of two on the Bangkok leg, one of five on the Cambodia leg, and one of about 30 on the Vietnam leg. I don't believe they do that on the Discovery tours, but you might want to ask. The largest segment of the tour was large because of a Groupon deal - and many who took advantage of the deal were not seasoned travelers. There were several days with free time, and a surprising number of people would not leave the hotel unless with the guide/group. I was one of the few who planned my own free time excursions (I thought the tour excursions were not cost/benefit worthy). The single supplement was reasonable, and I would definitely recommend you look into that as an option.
All-in-all it was a fine experience, but in no way comparable to a RS tour. I believe others on this site may recommend more Rick-like tour companies. I decided to use GAdventures for my next trip to Ecuador and Peru. I'm looking forward to comparing the two companies.