Hi 'rebel and welcome aboard! Hope we can help!
As you can see from my sig line, we have a KZ and its a 30' "5th" with one slide. We did a lot of research before we bought and have been very pleased with ours for the last 3 1/2 years. Its plenty big for DW and I and should be fine with another adult and probably even a couple more kiddos as long as you spend most of your time outdoors as we do.
I'd go with fiberglass as its lighter even though there is nothing wrong with aluminum. Many prefer it but I don't believe it adds much.
After looking at many others and owning one, I can highly recommend KZ. Ours has given us outstanding service with nearly nothing going wrong. Biggest problem I've had with it is a drawer guide breaking and KS sent me the part to fix it. My dealer would have done it but it was easier do do it myself then take it over for that small a repair.
KZ Recreational Vehicles: Travel Trailers, Fifth Wheels, Light Weight Towables, Sport Utility Trailers
Speaking of dealers, I would suggest looking at McClain's RV. They gave us a great price and service. Can't speak higher of them. Have a site:
McClain's RV - Home
On the other side, I will never own another Fleetwood product nor go near Vogt RV again

. PM and I'll be pleased to send a link that will take you to the gory details

.
Again, welcome aboard. Take your time and enjoy the fun of purchasing a new RV.
Happy Camping!
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Turn Key, DW & Tilly, The Camping Boston Terrier
'03 Chevy 2500HD, 4X4, X-Cab, Long Bed
'04 K-Z "Durango", 275RK ("Sunday Haus II")
Twin Kayaks, "The Ride" by Wilderness Systems
North Central Texas, Where The West Begins!