Outside van is really high quality, as is advanced RV. For us, anyway, the Outside vans were just too industrial on the inside. But, IMO, they're higher quality than Sportsmobile (who is doing our 4x4 build). SMB's interior options means you can get any feel you want on the inside. The costs with Outside van to do the same went up quite a bit. We're doing their interweave fabric + light browns and grays as we want the interior bright and open feeling. We love westy's and the semi-nautical feeling they have, and the current SMB's feel a lot like that. The outside vans felt more like industrial gear haulers and wasn't stoked on the metal cabinets since you can't modify them much like you can with wood. If you like Outside van's style, you can't go wrong with them.
One of the great things about SMB (and maybe others do this, too), is that you can custom order your van through SMB with the option to finance the van+build on a single RV loan. 2K downpayment to hold your spot in their line, pre-approval just before the build with 10% down to the lender, and off you go. 15 year loan around 5% interest. I can't imagine having 130K tied up in an asset that is depreciating, so this worked out perfect for us.
We toured the SMB Fresno facility, and were happy with the the details. We also toured the Earthroamer facility, and I feel like that's the other end of the spectrum from a price and quality standpoint. The wiring looms those things have is a work of art. Advanced RV is up there with their interior builds, but IMO, are in a whole different price league compared to SMB. For us, the design freedom, cost, and interior style made SMB an easy decision. But, I really don't think you can go wrong with any of the major builders out there.
I'll throw out My Tourig as another builder. Spoke with these guys extensively on the phone, and they're a great group of guys. Would not hesitate to spend money with them. They're likely the shop we'll go to for modifications.
http://www.mytourig.com/custom-work/