Hi! Just started running oot 3ds on my old 3ds from 2011. Should I upgrade to a new 3ds or even new 3ds xl? Are there any big differents in running on either devices or should I be fine with my old one?

no you can use your old one just fine

the only difference is cartridge vs digital, where cartridge is slightly faster

Will I notice it in game or is it just in general? I guess it would be sweet to have a bigger screen though :/

I start with this one and if I still running it in 2019 I will consider buying the new 3ds xl :D

it's about a second for 5 loading zones