What size boat...budget...single handing or with crew?
In my opinion, the smoothest ride is in full keeled, heavy displacement boats. It is also the slowest ride. Everything is a compromise.
I would choose NON cored fiberglass hull (below the waterline) for most cruising destinations and Aluminum or Kevlar/aramid/composite if I were heading into FAR northern waters.
MUST gadgets: depth sounder, GPS, VHF, EPIRB, LIFERAFT, RADAR (SSB or SATPHONE for offshore), windvane (for offshore)
Nice gadgets: auto-pilot, chartplotter, wind-indicator, PACTOR E-mail, Furling sails, generator, watermaker,
No longer posting. Reach me by PM!