Well... that all depends upon several factors:
What Year?
Which Engine?
What configuration (true duals, x-pipe, 2-1, etc.)
Any existing mods?
Planning any mods?
What's your budget?
What's your driving style?
What are your preferences (ie: do you want loud, do you have any concerns regarding drone at highway speeds, etc)
"Nicest exhaust note" is a fairly arbitrary & highly debatable topic. Opinions vastly differ, but if you get a little more specific regarding your preferences & intended use, you will get a bunch of opinions (and likely start a friendly argument!)
I have an '01 with the 8.1L big block 496... I prefer a nice growl during acceleration, but don't want to wear earplugs while driving down the freeway. I don't like the 'rasp' that Flowmaster typically gives on the top end, but still wanted to turn heads when I hit the gas.
I went with Doug's Headers & Dynomax exhaust... I have no regrets!
Best advice I can give you is to get a good set of headphones & search for audio clips on YouTube... although everything sounds different in real-life, you can get a good idea of how your truck will sound after the install by sampling audio from similar setups.
That's the route I took & was able to narrow the field down to Dynomax & Magnaflow.
JBA, Gibson, & Flowmaster all had a nasty rasp on every clip I sampled.
Hope this helps