The Google Nexus 7 is smaller, with a 7in display, and aims at a similar market to Amazon's Kindle Fire.

But the huge volume of apps available on the iTunes App Store could help users make the decision to choose a cheaper iPad over competing devices.

Apple's large chain of retail stores is also a benefit for the company. Google will be selling its Nexus 7 from its online stores only, and Microsoft only has 20 retail stores and its online store to sell the Surface from.

The rumours of a 7in iPad continue to be viewed with some scepticism, however, as the late Apple co-founder, Steve Jobs, dismissed the idea: "The 10in screen size is the minimum size required to create great tablet apps. 7in tablets are tweeners: too big to compete with a smartphone, and too small to compete with an iPad," back in October 2010.

Microsoft founder in the future, but is very excited about Microsoft's new tablet, he said in an interview this week.