Stock 40 IDF is 28mm. I put 34 vents(max size) in 40s on a 2109 and it really woke up the upper end without softening the low and mid-range.
44IDF stock is 36mm.
I believe 45DRLA have 38mm, but not 100% sure about that.
Like you Al, I'm not convinced of the supposed Dell superiority. Other than WOT high-rev racing or dragstrip usage, I'll submit nobody can tell the difference on the street. I can't take the Pepsi challenge anymore since I switched from carbs to EFI. But I don't think my 44IDFs left much if any performance on the table on my 2165cc type1.
Vents are available up to 34 for 40 IDF and 38 for 44 IDF. Every part is available for Webers new, today. That is a good enough reason for me to stay in the Weber camp.
Every part of the equation has to work together: carbs, intakes, heads, cam, rockers, exhaust, compression, and yes, even the trans ratios and vehicle weight. If everything isn't sized properly the resulting combo is meh.