I am purchasing a table for sorting my collection of LEGO pieces. Can others chime in on what color might be preferred for the table top? The table I am looking at has a stained oak effect top vs a completely white top as an alternate option -- which do you recommend? Also, any thoughts on getting a table with adjustable height vs fixed height? Thanks!

White works best, as it bright and neutral colour.

I very much like my smooth white non-reflective laminate surface with dark wood border kitchen table, it's my favorite especially when it has a couple thousand LEGO pieces on it. I also like to have a smaller TV tray/table next to me for instructions and or built up modules. 

White usually works well, but I think any lighter color is OK.  With what you show there, I think it'll be fine as it's both a fairly light color as well as having a bit of texture which will actually make it easier to see pieces (vs a small tan tile becoming camouflaged there if it were a similar solid color).  One thing I do while sorting is put a big scoop of the batch I'm working with onto an inverted large white Sterilite lid (from one of my larger storage bins) and then work off of that wherever I'm sorting.  Obviously a nice high-contrast for visibility of the pieces, but the lip around the edge of the lid where it goes over the sides of the bin helps keep any small parts from escaping.  

As to your other question- if you have the option for an adjustable height table, I find it's always nice to have some variety in position if you're doing a tedious task like sorting for any longer period of time.

I prefer not having a hard surface for sorting, less chance of pieces rolling off the table.

My desk is black, with a black IKEA mat on top so I can rotate whatever I'm building without scratching the finish on the desk. No problem sorting with a black table, I'd just get whatever table I think looks better in the room.