TRIMRANGE, dot operator, or other?

What is the best way to apply formulas in column C that simply concatenates all of the data in columns A and B, but expands if columns A and B go from 50 rows to say 60 rows with new data so you don’t have to drag down formulas? I have headers in row 1. I’ve been using in C2: =DROP((A:.A&B:.B),1). Now with TRIMRANGE, I can do =DROP(TRIMRANGE(A:A)&TRIMRANGE(B:B),1). However that seems no better with this newer function, and if anything a lengthier formula. What’s the best way to do this?