It really is a personal decision. Out of 7 or so 128gb imgâs Iâve downloaded and tried out, not one has made me happy enough to stick with them. I think the user needs saveable options to change the pi img to suit your needs, and not one of them yet has allowed me to do this successfully.
Iâm starting to think I might create my own from scratch which suits my taste.
As far as speed is concerned, just make sure your micro SD-Card or external hard drive is at least 80Mb/s read speed and fully compatible with the pi3, Iâve found that 64gb imgâs transferred to the 128gb microSD Card seems a better option, as you can then extend the size manually, then add further roms of your choice to suit you, later on.
Â§Â§check here -Â https://elinux.org/RPi_SD_cards