Should I buy a 256gb ssd+external drive or a 512gb ssd model?

I'm thinking of getting a m4 MacBook air and the cheapest one available is a 256gb model. Should I get the 256gb model and use an external ssd that I already have or buy the 512gb model. I mostly do graphic design and use programs such as photoshop, illustrator, and Indesign. I used a 2019 MacBook air with 128gb of storage+external ssd up until last year and it still worked fine before I switched to a Windows laptop.