9/10 its the bread. It will make, or break a sandwich.
That said, i am terrible at bread making..... 
For sure. The bread for tbe deli sandwiches at Bay Cities Italian Deli in Santa Monica is made onsite and it’s spectacular. My second favorite spot, Dan’s Super Subs in Woodland Hills has their bread made by Agostino Bakery in Oxnard. They’re different, yet perfect in their own way. Bay Cities’ roll is hard on the outside and it has that beautiful bubbling/blistering, yet it’s soft on the inside. Dan’s roll is soft witn sesame sedds, but it’s never soggy.