I would say the 19' Mariner. I too have a Day Sailer II, but I also have a 1973 Mariner (and a Rhodes 19). The Mariner, like the Day Sailer is still in production which means parts (if needed) are readily available from the current Builder, Stuart Marine and from D&R Marine. The Mariner Class Assoc. is an active group with a good forum. Association membership is $15 per year. Also, like the Day Sailer they are a "one design" class, which means basic specs don't change over time, although there are some appearence changes as can be seen with Day Sailer I's, II's, and III's.
The Mariners have been in continuous production since 1963 to present. They are available in both a centerboard model and a keel model. The centerboard model has a 10" draft with the board up, 4'-11" board down. The keel model draft is 3'-3". The keel weighs 315 lbs. Sail area is a 185 sf. The mast is deck stepped.
As for the different years, as to which is better, I prefer any of the 2+2 models centerboard models which date after late 1968. The pre-Stuart Marine Mariners had a 165 lb. iron centerboard with 200 lbs. of lead ballast along the centerboard trunk. The Stuart Mariners use a 70 lb. fiberglass centerboard with around 300 lbs. of lead ballast (might be wrong on the lead ballast).
The boats from 1963 to early 1968 had a cabin with two berths, head, and stove area. It had no cabin bulkhead (there are kits to add one). The cabin has a stepped appearence with a forward ventilation hatch. There is a wood deck in the cockpit and cabin. There is a deck overhang in the stern (similar to a Day Sailer I). There are wood coamings along the cockpit. There is a ice box molded into one cockpit bench with a storage hatch on the other side.
The boats from late 1968 to early 1972 are the first of the 2+2 models. The 2+2 model went to a 8.5 foot fiberglass self bailing cockpit (similar to a DSII cockpit) with fiberglass rails with a wood cap. The bailers are above the waterline at the forward end. The cabin is enclosed and has an entry hatch. There are 4 berths in the cabin, a V-berth (for 2) and 2 quarter berths that extend under the cockpit. The V-berth is open, with a arch under the mast as a support. There is also a place for a head, a water storage area, and a sink. In the cockpit, there are two large storage lockers and an icebox in the stern. The cabin is still stepped in appearence and has a forward hatch.
The boats from late 1972 onward including the Stuart produced boats have a redesigned cabin that did away with the stepped appearence. They also did away with the forward hatch. Inside the cabin is the same as the previous model, except an icebox was added. Also the support arch was replaced with a compression post to support the mast. In the cockpit, there is only one large storage hatch (except for late 1972 and the 1973 model which don't have any hatches). I added hatches to my 1973 model.
I sailed my Mariner on the Texas 200 in June with 2 crew on board. The Texas 200 is 5 days of sailing / 4 nights of camping going about 200 miles up the Texas coast. We all slept on board. My crew destroyed their tent the first night and slept comfortably in the cockpit. I slept with the gear, supplies and coolers (including a big Yeti cooler) in the cabin. We sailed the Mariner thru some very shallow areas.
John