A cache will help your site load quicker, resulting in some Google goodness. Don’t leave performance on the table if you can get some for free.
Not all cache plugins work equally well and may provide different benefits depending on the structure, content, and theme of your site. When deciding on a cache plugin you’ll get better understanding if you make a number of comparisons between cache solutions using a performance reporting site such as Pingdom tools. Pingdom allows you to select the location of the test so pick a centre in a region close to your hosting so as to eliminate unnecessary network issues.
There are are performance analysis sites such as GTmetrics and Google PageSpeed Insights that you might also want to try out.
If your performance report identifies any other issues that aren’t related to caching, then you will gain even more performance if you investigate and resolve those as well.