In a thread that's now gone, someone posted a reference to an AISC document addressing bolted & welded connections. Perhaps they could post that again.
Welders are typically more expensive per hour than your average construction worker, and welding takes longer than bolting.
On the other hand, welded connections are better where deflections under dead load might mean bolt holes won't line up (crossframes in curved or skewed members), or where the connection is hard to match exactly (like splicing rolled sections where mill tolerances lead to thickness differences or nonalignment of flange & web). If the splice will be architecturally exposed, welded might be considered to be more aesthetic at a distance.
You want comparison of field vs. shop, or bolted vs. welded? Bridge or building application, or doesn't it matter?
Field vs. shop--just about everything is easier to do (and less expensive since time is money) in the controlled environment of a shop than dangling in midair. Your limits are how big a piece can be transported & handled.
