Not a stupid question at all, it's an old argument, one for the ages.
Both would be correct for the 109 and any other aircraft designed by Willy Messerschmitt under the auspices of the Bayerische Flugzeugwerke. The 109 was conceived, designed and built while the firm was still known as BFW. (Willy joined BFW upon a merger with his own company, Messerschmitt Flugzeugbau.)
In 1938 BFW incorporated the company as Messerschmitt AG. All aircraft designed before this period carried the prefix of 'Bf', while those designed after carried the prefix 'Me' before the design number.
The two prefixes were used interchangeably on all levels within the Luftwaffe as well as the German aircraft industry during WWII.
For a more detailed explanation go to the
109 Lair and click on 'Articles', then 'Bf or Me - An explanation'.
As to good kits in 48th, you can't beat Hasegawa or Tamiya, although the latter offers only Emils.
If you want a complete collection of 109's, Hobbycraft is the only decent manufacturer which produces the early 109 variants; Berta, Clara and Dora. They all have fit problems of some kind or another, but they're definately workable. Their G isn't too awful bad, the only problem I ran into was with the canopy, the hood itself would not fit between the windshield and rear portion. Hence one of my rare excursions into the world of vacuform canopies...
If you're really brave, you could tackle Falcon's Bf 109G-12. They're the only manufacturer, that I know of, which produces a 48th kit of the 2-seater. But it's an ugly kit.
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