Wiwo Hercs, about 90% of my tactical flying served the Paras and about 10% SF, so I've worked pretty closely with both. Both are great to work with, but rather different mindsets. Paras very 'in your face', bold, brash etc about their operations, achievements, style etc - a requirement of their role as Spearhead really. Whereas SF, quite the opposite, quite, reserved, hard to get inf out of, full off hidden skills and linguists, medics etc.
No data is available, for obvious reasons, and because SF guys rarely discuss previous units, but it was widely known and accepted that the RAF Regt was a very fruitful recruitment ground for SF, because SF troops, as well as the brawn, require brains. Mostly brawn in the Paras, much more brains in the Regt, so find an individual who had both, and you had a good recruit wherever they came from.