well, the new ms office for osx is really good, so if all you need is web apps for business tools (erp, crm, etc) plus productivity apps a mac is the machine to go with right now.
mb, mb air, the small mbp are all excellent office machines.
switched personnally to a mba in 2012, wouldn't go back to a wintel notebook if they paid me.
No. It lagged about a year behind the windows version (2003->2004, 2007->2008, 2010->2011, no 2013 equivalent), for 2016 they should be both at the same time. Also, regarding the features, it used to lag, but since 2011 it achieved almost feature parity (minus the addons, that are downloadable extras, like PowerQuery, PowerMaps or PowerPivot).
mb, mb air, the small mbp are all excellent office machines.
switched personnally to a mba in 2012, wouldn't go back to a wintel notebook if they paid me.