The Mossie was used as a transport - they were sent to collect much-needed ball bearings from Sweden, which involved flying through German-controlled airspace, so speed and stealth were essential.
There was nothing wrong with the 'Tsetse' (the FB Mk.XVIII armed with the 57mm Molins gun). It worked exceptionally well. The problem was that it was designed for the anti-tank role but the RAF changed their mind about the requirement (shame really, it was accurate and powerful) so it was given to Coastal Command who used it in anti-shipping generally and anti-sub in particular. The gun was far more accurate than RPs but the plane was less flexible (you couldn't switch the payload) so the use was limited. They did shoot down some aircraft with the big gun, though - including at least one Ju 88! You can read about the Tsetse and see photos at:
http://www.quarry.nildram.co.uk/Molins.htm
You are right that the one argument in the Ju 88's favour is that it was in use throughout the War, while the Mossie only came in a bit later (but still before the USA did!). However, in every respect the Mossie could do what the Ju 88 could do, only better (the possible exception being torpedo dropping - the Mossie was never considered for that AFAIK).
Don't get me wrong - I like the Ju 88, it was IMO one of Germany's best aircraft and would certainly be on my top ten list of WW2's best planes. But it was very much 'jack of all trades, master of none'. And it was obsolescent by the end of the war (see Ju 188, also being replaced in some roles e.g. night fighter), while the Mossie remained the cream of the crop for years afterwards.
The Mossie came in four main versions:
1. P.R. - almost uncatchable, and the wooden construction made it hard to pick up on radar (one of the first stealth planes!). Also had a very long range.
2. Night-fighter; the best in the war (only the He 219 compared, and that came in very late and was very specialised). It actually operated as an escort fighter to the Bomber Command attacks, its role being to pick off the German night-fighters - which it did very well.
3. Bomber: it suffered only one-tenth of the loss rate of the Lancaster, and in winter the plane was so fast it was capable of two trips to Berlin in one night. Later versions could carry one single 4,000 lb bomb.
4. Fighter-bomber (with 4x20mm and 4x.303 in a solid nose, plus rockets and bombs): highyl effective and widely used in the ground attack and anti-shipping role. The Tsetse was a version of this.
Then there were the special roles, e.g. the bomber used as a transport etc.
The Mossie would get my vote as the best all-round aircraft of the war, by a comfortable margin. The Ju 88 was very good - the Mossie was brilliant.
Tony Williams: Military gun and ammunition
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