I think (as always) it depends on the work you expect to do Tifa.
I don't have vertical 'drilling' spindles on my mills (although they do have vertical heads) but if I only had a vertical mill for drilling, I might find it limited in space below the spindle (with chuck, drill bit & vice fitted) and not enough 'stroke' (only about 2"?) to cover all my needs.
My large Warco drill (benchtop 12 speed) is used for many things – including pre-drilling 4" fence-post bolting holes yesterday (it is used for both metal & wood working) and I have several smaller drills that get used regularly for various specific things too. I guess I could manage with just one tool (if I really needed to) but then I wouldn't have the convenience of choice.
So I'd go with the suggestion of storing the drill somewhere else and seeing if you miss it. If you've not touched it in twelve months time – then you probably don't need it – but if you have, then you may have found that your mill is not a 'solve-all' for your kind work.
Regards,
IanT