If you want to live in the city, I highly recommend Logan Square/Art Museum area or Rittenhouse if you've got the dough. I lived around Logan Square for about a year and I felt incredibly safe even late at night. Northern Liberties is a great place for brogrammers - it was a little too much for me.
DuckDuckGo is the coolest company around that I'm familiar with. Tech scene is good. Tons of meetups.
The Philly tech scene is small but dynamic and growing every day. For a sense of the scene, read Technically Philly and subscribe to the Philly Startup Leaders listserv [2]. The major clusters are Old City Philadelphia, home to N3RD Street and other related makerspaces, Center City, University City (near UPenn/Drexel), Northern Liberties as was mentioned. There are a bunch of suburban tech clusters as well, and the city is pretty evenly split between the two, I'd say.
There are tons of meetups in any given week on anything ranging from VR to Android to data. There are a couple of big conferences here every year including Emerging Tech for the Enterprise [4]. We also just hosted FOSCON. We have an active geek community in Geekadelphia [5].
Big companies (depends on what you think of as big): DuckDuckGo, Curalate, Linode is relocating here, Comcast is the number one employer in the region and is increasingly working on more cutting-edge tech projects (although obviously also still has all the features of a large corporate entity), Urban Outfitters down in Navy Yard. Then there are plenty of pharma , financial, and eds that make up the meat of the city's white-collar industry: GlaxoSmithKline, PNC, Temple, Drexel, Children's Hospital of Philadelphia, etc.
Where to live? A loaded question depending on what you value. Some people live in the city to be close to everything. The coolest neighborhoods right now are Northern Liberties and Fairmount, probably. Some people live in the burbs for the schools. Some burbs are closer and more accessible by train than others. Depends on what you're looking for.
Any more details, feel free to shoot me an email. It's my profile. I'm happy to answer questions!
[1] http://technical.ly/philly/ [2] http://phillystartupleaders.org/ [3]https://en.wikipedia.org/wiki/N3RD_Street [4] http://phillyemergingtech.com/ [5] http://www.geekadelphia.com/
First Ill talk about the main line, it is a great place to grow up/ or live if you are in your mid to late 20s. From Ardmore, Lower Merion, Bryn Mawr, Malvern, Paloi, Exton, and continuing on to King of Prussia have a lot of great places to live and a lot of companies. Espically in Malervn their is a large presence of companies. I take the regional rail train from the suburbs into the city for school and it is super easy and kind of relaxing.
In the city, certain areas of the city are blowing up right now and it really is a fun place to live. I lived around 12th and Spring Garden and apartments were being built in every empty lot and there are so many young people its a great place to be. There is so many great bars to go too and amazing restaurants throughout the city its awesome.
From what I can tell on meetup.com there are plenty of meetups for various technologies. The tech scene won't be as big as in boston, but it seems sufficient.