Is it more easy or difficult to manage technical staff compared to sales / admin staff and why is it so?

All it depends on education and sense of understanding,Sales and admin staff are qualified, they have capability to understand what u r explaining to them as compared to technical staff they usually take time to understand and hence they r hard to manage

I would say "It is easy to handle technical staff as compare to sales staff".
We have Standard Operating procedure (SOP) which give the direction for Technical Staff but on the other hand, rather very difficult to make any SOP for Sales people

Ashfaq: Although I have done more of technical management than admin+Biz dev management, I would say the former is easier.
As Masooque says, it depends as well.
Education and motivation is a key factor in all.
Usually and not always, admin job is bounded - meaning, there are said things to do and you need to know how to do it.
Sales guys, unless they understand the product well which to sell, they cannot do a good job - once they are ready to sell, they do not need any coaching - they just go after customers - more independent and less team play (like admin).
But for technical team management, lots of cultures and background collide as it is more a TEAM management and usually you attack more ambiguity wherein even leads or managers have not done what they manage earlier as technology grows faster on you, but you are finding best ways to get it done and hence it would like you have lots of opinions and directions to go after which makes managing harder but if you have the focus and buyin, the technical guys are easily to manage - they must be given the empowerment and freedon as well - only Innovations strives in technical field.