I no expert (far from it), but I currently own a 2014 ES-355, bought new in 2014, and paid roughly what they are asking for the -355 your looking at. I also have a 2009 -355 w/ Bigsby I acquired earlier this year. I think your main concerns should be the overall condition of the guitar and does it come with a money-back return policy. It's been my experience that -355s hold their value well.
There are numerous threads on here with pros and cons of Richlite. My 2009 ES-355 (yes, 355s are my fav) has an ebony board and there is a noticeable difference in tone between the two (same pickups in both). The 2009 is warmer and richer in tone. Is this because of the difference in fingerboards? I don't know as there is also 5 years difference in construction, as well as the 2009 has a Bigsby. But they are both fantastic blues machines.
As for -335 vs -355, the -335s I've owned were lighter in weight, and brighter in tone than the -355s. I sold my -335 when I acquired a -345 (with Varitone). The -345 is basically a dressed up -335 and most have the Varitone Circuit.
JMHO and hope you find this info useful