The Alfa's are fine with regards to reliability and are a different class to the vRS Fabia. £ for £ you will get a bigger and more solid car with more toys and credibility with the Alfa, but the vRS is an absolute scream!
We average 8 Fabia vRS alone per month and they are a hoot, but they are exensive and getting one 2nd hand is not a lot cheaper than buying one new. The Alfa's are cheaper (8v) and slower but the 16v if you can afford one is superb, better than the vRS.
My choice would be...
£8,000 - £10,000 2nd hand vRS
£10,000 - £12,000 New vRS or used 16v
Just be wary of the trim wear on the vRS and keeping the light coloured seat clean looks a nightmare! No eating chocolate!!