You'll find split opinions on this one - some prefer the 747 which has a slightly wider UCS and some love the privacy and space of the 'A' zone UCS in the nose of the 747 on the main deck (note many avoid the upper deck now since it was split UC and Y - also note that all Heathrow 747s have this arrangement, none have all UCS on the upper deck). Then again others prefer the A346 for the cabin ambience (noticeably quieter) and more modern look and feel to the cabin, but others find the long cabin less amenable than the different zones of a 747.

There are no double beds, VS experimented with this on early 747 configurations but that is no longer possible.

My suggestion - why not try both, do a 747 one way and a 346 the other (especially if either EWR or JFK works for you), then you'll know for the future?