PuraSan does cost less and uses less power
The PuraSan does cost less--typically at least $300 less than the new Electro Scan (current version of the Lectra/San)--but I wouldn't say it works any better, just a little differently. It uses only about half the power 'cuz it doesn't make its own chlorine, so it doesn't have an electrode pack. However, the chlorine cartridge, which typically lasts a year on most boats, costs close to $100 including HAZMAT shipping (which is why I don't know of any retailers who carry it, so you have to order it directly from Raritan)...which can make up the price difference in just a few years. And, it's not uncommon for the siphon check valve in the line from the cartridge to the toilet to get clogged up with salt or minerals, which can be a PITA to deal with. But it will work in both fresh and salt water equally well, so you can use it with both raw water toilets and toilets designed to use pressurized fresh water. Otoh, the new Electro Scan version of the Lectra/San is much easier to maintain than the previous versions 'cuz--among other reasons--the controller has LED messages instead of only blinking lights, and it uses less power than previous versions. So it's your choice. If you want to study the specs for both in detail, you'll find 'em here: http://www.raritaneng.com/products/waste_treatment/index.html