Gitzo Tripod purchase suggestion
Many people happily use 400mm (& longer) lenses on the 2541. That said, if you offered to pay the difference & carry it for them, I'm sure all of those same people would take the 3541 in a heartbeat.
Note, the weight & price differences are both very real: 1.4 pounds & $200. It's up to you & only you to decide where to draw the line in the sand on both of those issues.