One problem is "Putty" can include a wide range of products.
You have the "paint-like" Mr. Surfacer to the "clay-like" Milliput et al.
I believe what most people mean by "putty" is the "toothpaste-like" products.
I dunno, maybe its a nomenclature type thing!
In general the putty you use depends on the size (L,W,D) of the gap or seam.
Products like Mr. Surfacer for hairline seams, Milliput for large (as in you could get the handle of a paint brush in the gap) and Tamiya for gap sizes in between.
I have the following by groups:
Mr Surfacer
Mr Dissolved putty
Styrene dissolved in acetone (home made)
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Tamiya
Mr White Putty
Squadron Green and White
Bondo
3M Blue glazing putty
Evercoat
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Milliput
Apoxy Sculpt
Magic Sculpt
Green Stuff (you mix the blue and yellow parts till it turns green!!)
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I've been using these for years and cannot honestly say that within each group I have a favorite
This is by no means a complete list of what is now available.
What I would suggest is to buy 5-ish of the products and try each of them until you find the one YOU like the best. Fortunately most of these are not expensive.
Do a Google search and you will find almost as many nays as yays for any of these products.