if you use mineral fertilizer, it is mostly the same

the liquid is handy for pots and stuff, in smaller quantities. it usually is easy to mix just a small watering can.

the "powder stuff" needs to be measured more exactly and is more contentrated, for larger volumes of "feeding water". I bought that stuff when I had lots of window boxes with annuals,

now down to one, and I still have some solid fertilizer left, sometimes I use it to feed the Dahlias in a regular bed, more expensive, but otherwise I wont use it all on that one window box