what are the diadvantages of having complte access and core in layer 3 with eigrp as a routing protocol.
If i understand correctly you are talking about connecting your access-layer with L3 links. If so disadvantages are
1) Cost - L3 feature set generally costs more although the IP Base image on 3650/3750 does support EIGRP stub functionality
2) Less flexibility in terms of vlan placement. This is the biggest disadvantage in my opinion. You cannot extend a vlan across floors because your vlans are now contained within the access-layer. With careful design you can work around this but you need to be aware of the difficulties than can arise.
Of course there are advantages as well eg.
1) STP does not go over the uplinks from access-layer to distro layer
2) If you use redundant links from access-layer you can have automatic equal cost load-balancing.
There is no right or wrong answer as to which one to use, it depends in large part on your specific requirements.