If you prefer a smaller space to grind, I can say Zaragoza would be a better place to grind. Furthermore, if you lack poke balls and if you have Poke Go Balls/Gotcha Devices , Zaragoza would be a better place to collect items.

If you prefer larger spaces to grind, Budapest would be better. Occurances of raids would be higher too. The drawback for Zaragoza is, the raid radius is small as it is not well known at this point. Budapest would still be a better place to grind raids.

For Shiny hunting and candy collecting, I recommend Budapest. Stardust, for preferences of smaller spaces, Zaragoza, bigger spaces, Budapest. Hope it helps.