I’m familiar with the Option of typing any value on top; I use SD mostly with my IPAD und for me a picklist feels more comfortable; and yes, a list twice as long would be a disadvantage; I‘m using SD for VFR flying, so I‘d prefer the list with the x500 values
suggestions for a solution
1) list with two columns?
2) different lists depending on the preselection of flight rules
in case of VFR 1500, 2500, 3500 etc.
in case of IFR or MIXED: 1000, 2000, 3000 …
for some more Arguments see also