UDS lid/temp question

Got a question and was hoping one of the guru's/sages on here can help me out.
On my UDS I have both a flat lid and a Weber kettle lid. I have a hard time keeping temps stable when I use my flat lid, but with the Weber I get them to dial in and stay there with little to no problems.
Is it safe to assume that the dome shape of the Weber creates a better 'draft' for the intake/exhaust than the flat.
I know some will say to stick with the Weber then, which I plan to do. Just would like to know why so I can understand the UDS a little better.

Heres a photo of the flat lid:



and here she is with the Weber:




With the flat lid my temps jump all over the place and I have a hard time getting it to stabilize. But when I use the Weber I can get the temps dialed in and stabilized with virtually no problem. All I can think of is the dome is creating a better 'draft' than say the flats lid.