There are plenty of apps out there that will help you gauge your smartphone's performance. However, they are not considered as reliable as they used to be.
Apps like AnTuTu Benchmark, Quadrant Standard among others help you check the phone's hardware capabilities. But a lot of other variables are also to be factored in while judging the phone's performance. A brand new Samsung Galaxy S5 may give a better overall score than a 2 month old Samsung Galaxy S5 on the same benchmark app simply because the older phone is in use and has a lot of its storage and RAM occupied. Moreover, other installed apps on the older phone may restrict the performance and give you a lower score.