I've thought many times I should invest in a chess timer to help games move along quicker.
They're more expensive than you might think for an OK one. I'd just get an app on a tablet/smart phone and see if that could do before spending my money getting people to play faster.
Iím guessing the jousters are cheaper, nimbler, but not too hardy, while the turreted ships tend to be larger, slower, beefier, and less maneuverable? I'm also guessing that arc dodgers special pilots, upgrades, and maneuvers mean they coast a lot more and thus limit the number of ships you can field?
Yes and no, there's always exceptions to the rule. Jousting ships can get expensive (named pilots, upgrades) and arc dodgers can be big too (Dash Rendar dans le YT-2400) and cheap (generic A-Wing and Interceptor pilots), but you are mostly on point with those assertions.
Balance in this regard, will get you farther.
Some of my favourite lists are weird balances of the three tiers and some completely ignore them. Probably my most effective one is the YV-666 (Jouster with bonus 180 degree arc) and two Twin Laser Turret Y-Wings (very consistent but slow damage in a 360 degree arc). I don't know how well it would hold up in a tournament, but it's beaten some netlists flown by competent players so far. I also really like running full on arc dodger lists, though those only work out well when I'm having good flying days.
When factoring this in, and if in the end the costs for both X-wing and Armada were approximately the same, then start up cost wouldn't be as big an issue for me.
I know cost is a big thing for any hobby, but you've gotta enjoy what you spend your money on. If Armada is what you're into and there's no precedent in the group, get that and start with it. If the group takes to it but wants to skirmish as well then they can pick up some X-Wing stuff. You can always borrow their ships just like they will borrow yours for games at the beginning and if you like it go from there.