We were also originally considering the Terra, but didn't think we'd need something that size right now. I'll say the extra space would be great, but we really like the size of the Horizon. We've been able to get reservations twice now only because we're under 20 ft. It's easy to tow, easy to maneuver, and very rarely have an issue pulling the Ram in right in front of it.
We looked at Airstream, Lance, Ember, Little Guy, Grand Design, and another Jayco, but none compared to the quality of the inTechs. Not that those aren't nice, but we get gawkers and compliments everywhere we go. The big front window by the dinette alone makes it worth it for us. The wet bath is a bit bigger than others we looked at, and that little extra space has made it a non-issue for us.
You do have to get creative with storage and there are a handful of modifications I'd recommend for accessing some of the storage. The black/grey tank is combined and only 39 gallons, so that's currently a bottleneck to dry camping if you aren't careful with water use. We had a small leak from the shower area that ended up being a loose supply line, but no other issues.
I don't have the paperwork in front of me, but I think the Rover package was around $1500. I use the tongue rack to carry a Pelican case for some extra storage, and we lock our trikes to the back bumper, so those two options were worth it for us. Haven't had a chance to really use the lift and tires, but I suspect when we're boondocking out west later this year, I'll be glad I got them.
@mysticbus has a Horizon without the Rover pavkage and could probably give you some pros/cons from the other side as well.
We went with dual LP tanks, outdoor kitchen (refrigerator and grill), power tongue jack, and power awning. I can recommend all of them with no regrets. Only options we didn't get were roof rack because we wouldn't have used it and solar/lithium because it wasn't available when we ordered.