I currently have a 42/16 ratio which is freewheel. I want to convert to fixed, should I stick to the 16 or go with a 17?

Do you have any problems with the 42/16 now? If not, keep it. If so, go 42/17 and know that you are going to have to spin faster to get back down the hills.

I really don't have a problem so maybe I will just keep it. So basically the bigger the rear cog the more pedaling action you will have? Newbie question I know...

You will spin more for the same speed if comparing switch from 16 -> 17

The "normal" way to set up a flip flop hub is to have your freewheel one tooth larger than your fixed cog. The logic being that you're going to use the larger cog for for hilly conditions where you might want to coast downhill.

I like to have my fixed gears just a little higher (meaning smaller cog) than my geared bikes.

We need more information than that.

Can you climb ok in your present gearing? Do you spin out when going fast?

So based on that chart, if i currently have a 46 up front and 15 in back, it'd be best to switch to a 17 or 19 for the most skid patches?

+1

Having a freewheel option in a hilly area is a great idea.

42/16 is a good ratio for non hilly regions.

Whatever it is.. 42/16 or 42/17 you'll get used to it.

There's only a marginal difference in the number of skid patches, and bumping up 2 or 4 teeth is a major change in gear ratio.