Harmy said:

I think Ady said he'll make it so that Boba is Jango's real son, not a clone, and as Boba wasn't brought up by Jango since he was about 10, there is no need for them to sound the same, it would actually be very unlikely.

Interesting angle. I may have not stressed this enough in my post, but I actually only wanted to know from such a point of view where you would consider Boba a Jango-clone, no strings attached. No changes in upbringing, no differences due to being raised without growth hormones, etc...
Just plain old clones look and sound like their original. Period.

If you take in calculation the different upbringing and what-not, then of course it makes more sense for Boba not to sound the same as Jango.

Besides, I think we can all agree Wingreen's performance outclasses Morisson's by a mile (if not more).