What to use 2 t2.micro instances or just 1 t2.medium

I have a running EC2 t2.micro instance which I find insufficient. So, I want to use 2 such instances with a load balancer. Or, I can use a t2.small instance which has the features of 2 t2.micro instances. Would it be wise to run 2 instances and pay for load balancing or run just 1 double-sized instance and not pay for load balancing ? Or it can be the either way?