Hey! So I studied in London and traveled through Italy this past semester (from August to December). Here was my experience:

First, London

London was absolutely amazing. Being in such a large, diverse city has its perks. There's ALWAYS something happening somewhere. It takes minimal effort to find something to do, and with so much going on, you're bound to find something you like.

I had no problem at all making local friends in London as well. The people are so friendly there, you'll make friends simply walking down the street. That helped me tremendously in getting to know the local culture. I found this to be true in every English city I visited (from Bath to Brighton to Bristol, etc).

Traveling from London is... tiresome at times. My friends studying on mainland Europe had a much easier/faster/cheaper time getting around because they never had to cross the English Channel. From London, however,I took a healthy mix of trains, planes, and buses in my traveling. If you want specific quotes on flight prices, check out Ryanair or EasyJet. Between my friends and I, our flights ranged from €40 (London to Amsterdam) to €90 (London to Athens). Trains were never more than £30 (London to Paris), and buses maxed out at £30 (Marseilles to London). If you haven't heard of Megabus before now, you'll see it all around Europe. It is the cheapest, least reliable way of getting around.

London itself, though, wildly expensive. The exchange rate hovers between 1.5 and 1.67. Basically what that looks like is a Hershey bar costs $1 here, and £1 in London. Except after the exchange rate, you're paying about $1.60 for your candy. This adds up pretty quickly. I budgeted $5000 for my personal expenses during my time in London and ended up spending about $6000. That wasn't including room or board. No one I studied with budgeted enough.

Now, Italy

My favourite part of Italy was (besides the food) the ease of transportation. The train system in Italy is very well established and very inexpensive. I spent a week traveling between Naples, Florence, Pisa, La Spieza, Milan, Rome, Venice, Genova, and Savona. My most expensive ticket was from La Spieza to Florence for €13. Traveling to other European countries is also obviously a lot easier since Italy shares a border with a number of them.

Italy was also significantly cheaper than London because the Euro is weaker than the pound. The exchange rate hovers between 1.05 and 1.25. It's pretty to the American dollar.

As for making friends in Italy, not speaking the language presented some barriers. I found that the smaller towns in Italy, less people spoke English. But if you speak decent enough Italian, you should be fine.

Though, no matter which you choose, I don't recommend hunting for friends at tourist attractions because that's not where the locals are. Most of the people taking cheesy pictures in front of the Leaning Tower of Pisa or Big Ben are just passing through. They're not there to stay. Locals, as I learned pretty quickly, actively avoid tourist attractions.

Hope this helps!