I'd only go with a 3301 if you are ready/willing to accept the Tier IV Final claptrap. While the 3301/3901 haven't had as many issues as other models with DPF, I'd still avoid them if I had the choice. There's a reason the 2501 is so appealing and sells so well.
Edit to add: while the 3301 sounds a lot quieter in the video, I don't think the 2501 video sounds abnormally loud. It sounds like my
L3200 and
L3800 models I have driven, which sounded like the previous
L2800/3400 models. I think this is just a matter of the 3301's more restrictive exhaust plumbing acting like more muffler.
I'd be tempted to look into re-routing the exhaust exit on the
L2501 or changing to a bigger muffler. Before doing that, try to determine how much of the noise is exhaust noise versus general engine noise. Exhaust noise will pretty much be focused on what comes out the tailpipe.