We have BYOD policy. THe Standard issue from the company is Dell but we all use our own :-)
I personally own a MacBook and Lenovo laptop,
Most of the laptop brand have most of the feature(s) that one would require in a corporate as a standard features.
What you should specifically look for after sales service and support is provided. What is the turnaround time for resolution.
Try talking to customers who what been their customer for say 5 Years, 3 years and 1 year. Get their views on what to do ensure acceptable service limits. Also while renewing did they have re-negotiate any terms or prices etc.
Hoep this helps.