Yep agree, separate units.
Go Garmin on the GPS without exception.
Get a GPS w/ a fishfinder or vice versa if it ends up cost-effective and then you have a backup option.
It's nice having redundancy; 2 GPS's is almost a requirement. Without a GPS on an extremely foggy morning you probably can't make it out of the harbor.
I like putting one on the "navigation for idiot's" screen that's just got an arrow; on the other GPS I'll show the chart. Helps keep you on course while narrowing down the number of things to run into
.
Jon