Cayden, physics dictates the design of a whistle largely. There is a lot of similarity in hole size and spacing across good low D whistles.
I own a couple Burke Vipers and an EZ. I do not own an MK.
My suggestion would be to just stick with the MK and become accustomed with the Super Duper EZ Grip. That is the bbest solution in the long run.
How much easier is the stretch on a Burke EZ low D and is it a good low whistle for a beginner having reach problems on a MK Pro?
It's a modest reduction of stretch. Personally I think that having the rotating bottom hole on the for stretch issues.
What are the trade offs?
The Burke whistles are free blowing whistles. How're your lungs? They are really good whistles in my opinion but probably not at all like the MK in the breath department. I find them to be very flexible tonaly. You have to play it, it does not play you.
Is the E on the Burke super weak?
No, not really. Compared to what? We could quibble if you like splitting hairs.
Also, anyone know if Mike Burke stocks the EZ low D or if it is a special order? What is the wait time on a Burke EZ low D?
Ask Mike. Yes, he tries to keep things in stock and I've had deliveries in a few days to a few weeks. He builds in batches and to a schedule. So ask him. He's one of us, really, not a big corporation. So just ask him.
Personally, I'd suggest you stop analyzing options and get on with learning to play. Otherwise you'll be back in a few weeks asking about another low D. The MK is a good whistle by most accounts so "Love the One Your With", "Dance with the one what brung ya", etc..