DHCP, when set up properly, makes for less work. Reservations will have the DHCP server hand out the same IP to the same hardware (MAC address) when it asks. If you have a device that is from the dinosaur age that doesn't play nice with DHCP, then make sure you give it an address that is outside the DHCP range on the same subnet. ex: Some home routers use 192.168.1.100 to 192.168.1.200 as the dhcp range. Setting anything from 192.168.1.1 (or 2 if the router is on 1) to 192.168.1.99 is fine, as is 192.168.1.201-192.168.1.254 (or 253 if the router is on 254). However, by setting static ips, you have to remember those ips specifically to interconnect devices on the lan, whereas reserving via dhcp allows you to use local dns resolution to connect to devices via their hostname instead. In additon, you run the risk of ip conflicts from forgetting which device has what ip in an increasingly complex system, and if you change internet providers or routers, you have a lot of extra work to do to fix the network settings to get those static ips to connect.

Alternately, just use the link-local ipv6 address to interconnect on the lan. That doesn't change on most devices, as it is based on the MAC address, and is always reachable on the lan.