I only have one anecdotal observation--a Seattle batter, Wong I think--but I immediately thought the advantage will be significantly for the pitcher, at least for the first month or two of the season.
I haven't been to an MLB game in 5 or 6 years and watched only a handful on TV during that time so haven't seen a lot of slow pitchers (but seeing game lengths move past 3 hrs is proof enough), but to be honest, I thought batters' "adjustment routines" were even worse a drag on at-bat times.
Overthinking a bit, the pitcher ought to settle into his routine for the inning or more he's on the mound, whereas the batters who are up 4-5 times but also have to watch time & rush through their tics then go back to fielding won't adjust as quickly.
yea, all that based off a sample of one at-bat. I wonder if any stats sites will be able to track obp vs pitch frequency/interval.