Sooooo many variables.
What style blend?
What cut?
Is it for lunting?
Is it for a sit down session ?
Does tactile feedback in pipes matter?
How long do you wish the session to last?
Do you want 6 or 9mm filters or none at all?
See how complicated it can be?
Or otherwise just go to Savinelli's site or to another online dealer and see which one appeals to you.
Chances are if you stick with the hobby long enough you will by, trial and error, find the right fit.
I've got a couple of 321s that I really like. It's a smaller 320 without a filter. I have a rusticated one like this, and a smooth, as well.
NIce…all I have are 320's but have been curious about the 321….may have to spring for one.