I am biased, as I try and get to the big seat no matter what the occasion! Also, my honeymoon (many moons ago) did not require a flight as we were going to the Lakes!
At one stage, VS were boasting that the partition between the seats could be lowered. However, that would only apply to the 747-400, which has a seat at each window and a pair in the middle (4-across), whereas the 340 aircraft (being narrower) are only 3-across. Check with VS through their website or call centre. Whilst Premium Economy is good, you do not get as much sleep.
Of course, a good reason to go in Upper is that you can take advantage of the opportunity to gain the maximum amount of sleep before you arrive at your destination ...