Pocket Wifi while traveling in Sicily

Why do you think you need it? Do you have a smart phone? if so, you can use it as a WiFi hotspot if you have mobile data on the phone (e.g. buy a SIM, or use your phone's international roaming plan and share data to other devices with the phone's WiFi hotspot).

Last year I used a Dutch Vodafone SIM in my Android phone and used the hotspot all the time for my laptop, especially on trains, through Slovenia, Italy, and France.

These WiFi hotspots made more sense a few years ago before smartphones were so ubiquitous and international roaming and SIM cards become so cheap. I suppose in some cases where a group of business travelers need to share WiFi all the time together, it might make sense, but in most other cases with one or two people traveling with one, I just don't see the benefit.

I have an iPhone with ATT. I now I can get a plan through ATT. I was wondering which way is less expensive. In Particular I want to use my smart phone as GPS while driving across Sicily for two weeks, so data is my main focus

AT&T has two plans: a $60/month plan that includes 1GB of data or a $10/day plan that uses your phone on the same basis as at home (and only on the days you use it). You might find a pocket WiFi for a little less than $10/day, but I doubt it's worth the tiny savings, personally, for the extra hassle of one more device to carry around and charge up, the inability to use your phone normally, etc.

You don't need data for using your phone as a GPS, FYI. The phone can use GPS without a data connection. What it does need is the maps and directions to make use of the GPS coordinates. You can download maps "offline" ahead of time on WiFi in Google Maps and other apps. it's not exactly the same as the "regular" Google Maps but it works. I suggest you try it out at home first with your own home area map and see how it goes. Could be you could get by with 1GB in two weeks if you don't use data for the GPS and use the hotel WiFi most of the time with their $60 plan.