For many years, I was in the "purist" camp, and preferred my U to penalize from the technical enforcement spot specified by rule, then transfer the ball to the hash mark, if the ball was still in a side zone after enforcement of the penalty. But, after I got into FBS, it became apparent that such technique was a bit frivolous, and wasted time, for no really good reason. We had good umpires who were able to get the ball moved to the correct succeeding spot while the R was making his announcement. When the R finished his announcement, the ball was ready, the crew were in place, and we could get the ball ready immediately. Maybe not a lot of difference in real time, but it was easier for the Umpires, and it just wasn't worth messing with. Ending up in the right spot, and doing it efficiently, was all that mattered.
Hash mark it is.
Robert