Having a large disparity in average worker income across the EU, I don't think is favourable at all, especially at regional levels eg UK business being relocated to Eastern Europe may benefit the country it moves to, slightly (but won't bring wages to being on par with UK averages) but it can have a significant negative impact on the area the business moves from and thus on the wider economy of that country.
And of course anything that could further damage the role and strength of trade unions is not a good thing, because collective bargaining is crucial in realising a safe and healthy workplace, adequate protection of worker's rights including the 'right' to a living wage and decent terms and conditions. Lose that, and you start destroying people which is no good for any business in the long run. Ad astra per aspera
the "competitiveness" that it has gained by reducing wages is not so much an edge on Asian competitors as on European, and especially Eurozone countries.
Because that means -and I am convinced of it since a long time ago - that what is currently a problem is not so much the economic thesis that grounds BCE policies than the lack of cooperation between UE countries, which is a purely political issue.
The question you can address the voters is: Would you rather transfer fiscal and social responsibilities to the UE or die from internal wage war (delocalisation and so on)?
This could constitute a simple moto for the next european elections...and would give an innovative solution to the problem, instead of resorting to old fashioned (and outright dangerous) nationalism (such as present in Sarkozy electoral program for example).