Are Butyl Tapes Equal?

Where would be a good source to buy pure butyl tape or ernabond?

Consider using Eternabond. That stuff seriously sticks!!!

No, not all equal.

3 basic types:

1) Your basic cheap putty tape.
This stuff is junk and holds no place in an RV.

2) Poly-butyl blend. (IIRC, that's what it's called)
Better, but still nothing to write home to mother about.

3) Pure butyl tape.
The most expensive but the best choice. It sticks very well to all surfaces, never hardens or crumbles and remains pliable for years. And its a bear to remove. That's a plus, not a negative.

As you said, for a few bucks more a roll, get the good stuff. It is well worth it. I have a part roll of it in my box of goodies I keep in my TT and it is still soft and pliable in spite of being many years old.

I personally would not buy this type of stuff from Amazon. Chances are it comes from China and holds the same quality as their tires....
You may pay more, but find some good old Made in USA product.

This info is based on my experience from a bunch of years ago. Maybe they have something better now, I don't know.