It's just like buying any other piece of hardware, the more money you spend, the better off you are. My current laptop is a MacBook Pro with 16gb of memory. I run VMWare virtuals on it for SQL Server. My preceding laptop was a Lenovo W510 with 16gb of Memory. Both have multiple SSD drives for storage (the Mac has an external one). In general, you need to get as much memory as possible, fast processors, and storage adequate to your needs. That's it.

Going with a Mac is a big leap. I strongly recommend the Lenovo Thinkpad.