The two bikes your looking at are at completely different ends of the spectrum, in performance and price. You really need to ride both of the bikes before making up your mind. Both are good bikes for the price, but you need to look at the way you plan on using the bike. Fast club rides or ice cream rides? Long distance touring or around the block? Ive had a chance to put at least a few miles on most of the tandem recumbent bikes (and trikes) that have been offered for sale over the years.
The Screamer is probably the most popular recumbent tandem ever built. The base model Sport Screamer starts at $3499.00 It is a well designed bike and handles well, we have about 20,000 miles on ours and for the most part it has performed flawlessly.
The Sun EZ Tandem lists for just under $2000.00. It handles well for a long wheel base tandem. And for the asking price is really a good value. But if your looking for a "fast" bike you may be disapointed.
You may also want to look at the Barcroft Columbia, very close to Rans Screamer, but shorter. http://www.barcroftcycles.com/bikes.html#columbia
It has a nice ride, and the short wheel base makes it easy to handle.
Any other bikes you have looked at?
What bikes have you ruled out?
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." - Arthur Conan Doyle