Yeah it's a big decision with lots of +/-'s.
In the end I've decided that if I'm going to make such a major investment into helping transport the car I might as well get the most use out of it. Enclosed has a similar footprint to most open, unless you go real small ultalite. On an open you still need to protect our open top car from the elements in transport and debris and your paint can get damaged once you cover it but have it lose.
On the other side enclosed allows you to protect it from the elements, have all your equipment inside safe and the car safe inside at night, you can utilize it for moving and storage in meantime, you can crash in it for the night if needed and more. It's a higher price but you get a lot more out of it.
On the other side of the spectrum I still don't have a car I can to it with that I own. I've been borrowing vehicles to get by once a year for the tow here and there. Trying to setup my Volvo XC70 to tow this behemoth, and in theory it could/should but I haven't done the practice. Also has a similar official tow limit of 3500 or so, and enclosed being 1800lbs (aluminum) and car being ~1200 lbs I could theoretically do it at the limit.
By the time the tow car is being all setup we will likely end up purchasing a family SUV next year that will be able to tow it regardless without an issue.