Welcome to iRV2
Glad to have you here.
The Regal is classified by Fleetwood as one of their luxury 5th wheels. The Wilderness is categorized as mid-range. As with any rv, the differences come down to construction & standard features vs options.
If you go to Fleetwood's
website, you can compare both models side by side. There you can see what makes the models different. For example, the Wilderness is wood framed with wood floor joists where the Regal has an aluminum frame & floor joists. AC is an option in the Wilderness; standard in the Regal. Those are just 2 of hundreds of differences between the 2 models.
If you have any more questions, feel free to ask. Enjoy shopping for your new rv.