Best mountain bike for roughly £300

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I am looking at getting a new mountain bike for around £300, at the moment there seems to be 2 good choices, either a Viper TR 3.0 Hardtail Bike 2006 (http://www.chainreactioncycles.com/Models.aspx?ModelID=10845) for £280 or a GT Avalanche 1.0 2006 (http://www.chainreactioncycles.com/Models.aspx?ModelID=13839) for £340.

a) which one should i choose & b) are there any better alternatives out there???