It's easy to fix performance issues by adding resources to a VM, but even easier to over-provision in the process. Increasing VM density and total datacenter efficiency need not be accompanied by performance degradation.
If you already use NetBeans for Java or C/C++ development, then it should probably be your top choice as a Rails IDE as well. Delivering strong editing and navigation along with good debugging and profiling, it's a very capable and highly integrated Rails IDE. And it's free.