First of all, welcome!
This will depend on what terrain you ski on and how stiff said skis are. I'm your size (5'10" 205#) and enjoy stiffer, shorter crudbusting hardpack (78-85mm wide) skis in the 170 to 177 range. On soft snow days and in powder on softer flex fat and mid-fat skis (88mm and above) prefer lengths in the 178 to 190 range. Since they are softer they are less unwieldy in longer lengths and still quite maneuverable in tight spots (trees). They also provide added float in powder at longer lengths. I would demo all you can before you buy so you can see how you like different lengths. Your best bet is to find a demo shop on mountain that will allow you to demo many pairs in one day for one price.
My personal favorite is the 183 Gotama (105 mm underfoot). I'm still on the 05-06 model but I've heard the 07-08 model is even more versatile. It's a very good all mountain ski, skewed towards soft snow but very capable on everything else. When it hasn't snowed for a few weeks you'll find me on my 171 im78's (78 mm underfoot). However, I've found that I enjoy my Gots so much that I'm contemplating moving exclusively to a stiffer mid-fat like the 178 Dynastar Mythic Rider (88 mm wide) or a pair of 183 Stiff Bro's (99 mm wide) and selling my quiver. Hopefully by this time Monday I'll have demoed the Bros.