Had my Novitec for around 18 months and it's a noisy bugger I'll tell you that! Certainly not an unbearable level of drone, in fact there's not much at all despite the 3" bore stainless. Just like gricey said drop your rear seats, and for an even more hardcore sound; wire the sound proofing flap open near your carpet pulley in the boot, believe me the pops and bangs become very 'real' with this set up!
The bombardone tailpipes are gorgeous and it has smaller bore pipe & thinner stainless so sounds very raspy, then again my Novitec has become very sharp and evil on cold start, especially after putting plenty of miles on it.
Either are an excellent choice - my friend has a Bombardone, I think it looks great with the acute angle slash-cut tips and MM elaborazione engraved tailpipes. You also get a lot of little pops and crackles with barely any effort, plus there is no drone at all to speak of.
The Novitec is for the more hardcore driver I would say, it lets off ear bursting pops and bangs; the loudest (103Db @ 1m) I've heard from any Abarth exhaust set up with standard center section/cat. The tailpipes are very nicely done but perhaps more subtle/German in their design with rolled tips, softer slash-cut angle and simple Novitec logo etched on each tailpipe.
So basically it's Italian flare and eye-catching design vs. German simplicity and lots of noise
Each to their own in this case, both are fantastic value and will catch the attention of onlookers. I'd say that if you have kids and can't adopt a 'full-on' noise approach then the Bombardone is certainly more user friendly, but if noise is your game then go for the Novitec; it's a riot and will make the most bizarre & random thumps, crackles and bangs you've ever heard for no reason at all - 3 car alarms have gone off due to such exhaust activity.