Since this post we've rented a 23ft International Signature with Queen bed and we liked it, but found it too cramped side to side to change diapers and whatnot. We also fully realized that we want to be able to camp in places like Boreas Pass outside of Breckenridge a few times a year. So we could either go big with a 27ft international to give us enough room to take care of kids or we could back down to the Basecamp and get the Grandparents to babysit while we travel and stay in cool places like Boreas Pass. We opted for the Basecamp option while our kids and future kids are too young to remember these trips anyway. We may eventually trade in for a 27ft when they get older. Gonna try to get the Basecamp this week. I ordered a Eazlift WD and Sway hitch 800lb tongue at from Amazon which should come in Tuesday. Hope to pick up Wednesday, we'll see.
I likewise rented a 23' AS on our maiden trip with an AS. While it served us well for our week long trip for my family of 4 (kids then 2 and 5 at the time), we likewise found it cozy. The other big thing that jumped out at me was water capacity (23 fresh, 21 grey, 18 black). We were still new to the experience, which is to say we probably weren't conserving very well, but we needed to fill and dump every 2 days.
From following various RV boards, it does seem the natural progression is to up-size. Some switching up 2-3 times.
When I bought, I focused on tank size. Also leaned on slightly larger than slightly smaller in trailer size. For Airstreams at least, their widebody (8.5ft width) starts at the 25' and up. Shorter ones are either 7.5' (<20') or 8' (22'/23'). Those half foot increments make a huge difference internally, much much more than it would seem.
After traveling in my 28FB AS the last couple years, it's a great size for us. It's basically two rooms (family and bedroom on either end), so there's enough space for people to escape into their own corner. I can say we'd be happy in a 25' also. AS's measure their lengths differently than every other manufacturer, as it includes bumper to couple. Versus all others that are quoting trailer body size.
The AS's do give up some functionality for vanity. Their curved bodies result in less storage, especially external storage.
Travel trailers are a very personal choice when it comes to preferences and how we use them. I think a Basecamp would be more than awesome, if boondocking and travel deeper into the backcountry is a priority. That when paired with a nice ground tent to host a family of 4 between Basecamp and tent would be absolutely workable in my mind (as I do a bunch of tent camping too). It would encourage more time in the actual outdoors rather than holed up in the TT.