Both those PC's have a GTX 550 TI which is not a particularly good graphics card. You should be looking at a 560 Ti minimum or an ATI HD 6870.
Overall the Dino PC I feel is a better choice. By changing the graphics card to a 6870 increases the cost to £629. Adding the 560 Ti which also means upgrading your power supply to 500W brings the price to £661. To be honest you really should not have less than a 500W power supply in any PC these days.