I have not sailed the "Sunshine" but did sail this ship 3 times the first couple of years it was in service as the Destiny.When it first entered service, it was at that time the largest cruise ship out there, at 101,353 tons. It had a passenger capacity of 2652 with a crew of 1150.
Since the overhaul and refitting, name change, etc, the tonnage , or size, increased very slightly to 102,853, and the passenger capacity jumped to 3006, with the crew remaining at 1150.
The Dream is somewhat larger at approx. 128,000 tons , 3652 passenger capacity and a crew of 1369.
I've sailed the Dream twice , with a cruise booked on it for Jan.
Everyone is different in what they want and expect but I have not really seen anything on the Dream that would get me to cancel or change my plans, if the itin., etc. were the same and you had the same type accommodations you would have had on the Sunshine.
As far as being crowded, if you look at a ship of approx. 103,000 tons with 3006 passengers and a ship at approx 128,000 tons with 3652 passengers, I can't see there's a lot of difference as far as being crowded.
To each his / her own, but you always hear good / bad things about any ship. If you want to cancel and change ships or cruise lines, I wouldn't necessarily do it because the Dream is " so big "--there's not that much difference when you break it down.
The thing I don't care for on the Dream class ships is that promenade going all the way around the ship and instead of being flush with the sides of the ship, it juts out, then the life boats are hung on that so when you look down from your balcony, you'll not be looking directly down to the water, but directly down onto the promenade deck. That's a minor thing and has not kept me from sailing on the Dream but if I had a preference, I'd rather they made it flush with the sides of the ship.
I would think you would enjoy the Dream, but as said, we all have our little likes and dislikes. Whatever you do, have a good cruise.