Thats a good question.
Firstly: Is your main usage browsing the web and other "tabletty" things like email casual gaming etc? If so I can say the Surface 2 is a fantastic device. I connect to my 24" monitor all the time browsing the web and such. I even write Word documents and make Powerpoint presentations with the Surface 2 (Its very fast, playing a 1080p movie on the monitor while browsing and having twitter open with the snap mode is no problem at all).
Second: If you do not need the tablet to be super portable (ie. you mostly use it at home or in the office) the surface is still a great option. Mostly because it is more powerful and can run legacy apps (sure you don't need it, but for the price its a nice addition to have). Speaking of price, seeing as the Surface Pro is cheaper than the Surface 2, it really depends on how portable you need it to be. The Surface 2 is a fantastically portable "PC". I use it for work (I fly alot) all the time and the long 10 hours + battery life and how thin and light it the Surface 2 is excellent.
So in the end, if portability is unimportant, I would go for the Surface Pro, if you need it to be portable then Surface 2. Make sure you get the Touch Cover 2 (its alot better than Touch Cover 1). Or again, the portability question: you can also get the Type Cover 2.
Both devices are fantastic. For me personally, because I use my Tablet for Work/University and I need it to be portable, the Surface 2 was the better option. That and I don't need Legacy apps. Office 2013 is all I need, and for anything else I have my desktop PC.
Hope this helps!
If you have any questions feel free to ask!
Sent from my Surface 2 using Tapatalk