Well if its a question of upgrading to i5 from i3 yes its worth it i3 is dual core and i5 is quad.
That is incorrect for mobile Intel CPUs.
All mobile Core i3 and i5 CPUs are dual core CPUs. The primary difference is Core i5 CPUs have Turbo Boost which can automatically increase the clockspeed of the CPU as long as the temps are not too high. Both have Hyper Threading.
The only quad core mobile Intel CPUs are specific models of the Core i7; "MQ", "HQ" and "MX". Mobile Core i7 CPUs without those designations are dual core CPUs.