I'm putting together my first SS/Fixed using an old Miele Roadie. I'm looking at starting with 70 gear inches. This can be achieved many ways with different chainring and cog combinations: ex. 48/18 42/16

Is there and reason, good or bad, to chose one set of gears over another. The only reason I see using a smaller front chainring combo is when moving up or down rear cog, it isn't as big of a jump as using a larger front chainring.

Any thoughts? Surrounding countryside is flat and I won't be using bike as an urban commuter.

Canflyboy

'06 Brodie Quantum hybrid
'07 Brodie Romulus cyclocross/commuter
'08 LeMond Tourmalet Roadke
?? Miele Project

Smaller chainring and cog saves weight. Bigger chainring and cog are more durable (more teeth, larger radius)

Don't stress about it. Pick a crankset you like and go from there.

like mentioned above, fewer overall teeth on a drive train increases strain on the parts, in theory, should reduce friction a little, and obviously eliminates a little weight, but decreases drive train life span at the same time

larger gearing does the opposite,

but.. more importantly you should be looking at skid patches if this is a street machine, go with a 17 tooth cog and you should be getting a lot more out of your tires,

yeah wouldn't really matter unless you're going to do some serious miles.

The larger chainring/cog ratio will last longer, will have slightly less friction and you don't have to have chain tension as tight. If you're doing a conversion, chainstay clearance may be something to consider, but i wouldnt worry about it unless you're going have something +50 teeth.

Sheldon brown mentions this about halfway down here.