I find a difference between giving 10x2 second exposures and giving a single 20 second exposure with my Omega D2V enlarger fitted with a 75 watt Photocresenta bulb.
The intermittent exposure sequence includes 40 moments when the bulb is dim and red and non-actinic and 20 intervals when it is bright and actinic. But the difference is surprisingly (!) small. The resultant gelatin-silver photographs from either method can be eye-matched by a small change in room lighting. In practice the time adjustment I give to compensate for final dry-down (typically 8%) swallows the small intermittency effect.
For me, it depends mostly on your tools and individual working style, but for the record I've never experienced any qualitative difference employing either style of printing. That may be because my exposures are always quite lengthy, any small differences in the amount of light delivered to the paper being ultimately negligible. Where it can make a difference is in the ability to keep track of dodges (particularly) and burns incrementally (i.e., 10 x 6 secs (total exposure) – 2 x 6 secs (dodge first area) – 1 x 6 secs (dodge second area) + 15 x 6 secs burn, and so on). Combined with a footswitch for the enlarger, one never needs to interrupt the process, or take eyes off the print during exposure.
Originally Posted by fralexis