Dell is better. While the CPUs have similar performance, the Celeron 2955U, being an Haswell CPU, have better Integrated graphics. I think you should be able to play it. But, It'd be better to buy one with at least Pentium CPU.
With every new generation of intel, there's an increase in battery life... So, logically the Dell should have better battery life... But, it also depends on other factors. However, there won't be much difference between the 2 in terms of battery life.