We are often asked what is the difference between the SV-35 and the SV-27 and which one would we recommend.
We always recommend the SV-35 over the SV-27 due to the following factors.
1) SV-35 has 35,000 cc/hr of powerful mosquito attractant vs. 27,000 cc/hr for the SV-27
2) The SV-35 has wheels so it's easier to move around.  (this alone is worth it)
3) The price difference is negligible between the two. For only 40 more dollars you can get the top of the line Skeetervac.
That being said, BOTH are very good units.  We personally use/test/run each each and every model that the manufacturer produces and sell only what we consider to be the best of class.