If you are/were relatively happy with your first Ijust why not grab another?
The Pico is a fine
device and might be a nice step up for you. However once you add a couple
batteries and a charger on the side it will be more costly. You will also need to learn the different functions of the device, learn about different coil types as well as battery and charging safety.
If you are okay with the added cost and complexity go for it. It is a huge performance gain and you'll be able to fine tune/adjust your vape to what you like.
If you like the plug and play aspect of a device you are already familiar with? Stick to the Ijust. Cheers.