I agree with Neil.
For a regular car (which is what 99% of people on here would have) sure a regular tandem trailer will do the trick for a few times a year. However for a specialised track car (neils radical or my aussie for example) that doesnt have windows or a roof and is held together with bonnet pins or clips you really just cant leave them anywhere out of sight let alone when the sky opens up, especially if it is an overnight stay. Having the ability to have tools and equipment permanently fixed inside the enclosed trailer just makes life in general 1000% easier. I'd really like to go interstate, but wont be booking anything until I have an enclosed trailer.
Many companies are making enclosed trailers now that are only around 1.5m in height with a popup roof, ideal for many types of cars, the downside is you cant walk in them. However they are lighter and more aerodynamic.
I've been looking for a while online, ive been looking even longer at every track event I attend (probably look at trailers more than the on track action). Atleast 50% of the trailers I see at track events I wouldn't even use to carry a ride-on lawnmower let alone a 1.5ton vehicle, they are just pure death traps.
My Aussie will fit in my pantec truck, but no hope in hell of actually getting it in there, i'd need 45 metre long ramps.