[stevee8]

Welcome to the forum.
If you haven't already done so I suggest you do a search on here for previous posts - that will give you some background on both makes. Attending a local Cobra meeting & chatting to owners might also help your decision whather it is about these or other makes.
The Python has not been in production very long & I think the car you refer to is not only their demonstrator but also their prototype so you would need to take a view on whether an early build of a new car is your best option. There are (or were) some in the process of being kit built, with posts on this site. You might also want to consider backup for RVD specific parts as they were (are?) being made abroad.
The Sumo is made in the UK, has been in production for some years & there are many more owners around who would be able to help if you needed it. I assume Pilgrim have done the factory refurb ? If so I imagine they would be able to tell you exactly what they have done which might be useful to know.
You may find an existing owner locally who would be prepared to look at the cars with you & offer advice. Good luck with your search.
Don't forget you can join the Cobra Replica Club online too !!!