You can get 2 cores from either our standard 4GB droplet for $20/mo or on our optimized 4GB droplet at $40/mo.
Standard droplets have shared virtual CPU cores. This means that your cores are shared with other droplets on the same hypervisor. Usually this doesn't pose a problem but if you will have a computationally heavy workload it may be impacted. If you have a background process that requires a good amount of CPU use constantly we'd recommend the optimized plan.
Optimized droplets have dedicated virtual cores. The vCPUs assigned to your droplet are exclusive to it and not shared. This ensures the the full processing capacity of the vCPU is available to your droplet at all times.
In deciding which to go with you can ask yourself a couple questions:
1.) Will this app or service require constant or nearly constant CPU use for background tasks (if yes, go optimized)
2.) Is the workload extremely time sensitive requiring millisecond resolution on results? (if yes, go optimized)
3.) Do you plan to do occasional high CPU activities like building software? (If yes, the optimized droplets will likely result in faster builds so in this case it's a time vs money question).