$400 per person or total? IMO, go for the cat. 6. We really loved having the verandah and did use it almost everyday. On the other hand, if you anticipate rarely being in your room then save the $$ for other fun stuff. All depends on your preferences.
It all depends on your needs. If you are going to spend alot of time in the room (small children who may need to nap, etc.) I would definitely consider a verandah or at least a porthole. We are sailing on the Wonder on January 27th and have booked a category 11 stateroom. For me, the outer staterooms weren't worth the cost.
We sailed in Category 6 with DD4 and were grateful for the verandah. While she napped, I could sit outside and read/relax. We also took advantage of room service breakfast each day and ate it outside. It's nice if you're an early riser -- you can sit outside and enjoy the ocean before everyone else is up!
We have cruised twice and we have two young children. Both times we had a verandah and I used it often as the kids napped and frankly went to bed reasonably early. We had coffee out there in the morning and I could read a book out there while the kids napped. Both cruises I had at least one child asleep during the sailaway party, so I sat out on the verandah as we left Port Canaveral. I was sad to miss the party, but it was nice to have an outdoor spot to enjoy the day. I guess if you are just adults or traveling with older children and don't plan to spend much time in the room it wouldn't matter much, but I enjoyed the private outdoor space very much and it was worth the extra cost for our needs.