A hard but good question, I have had an 360 for 4 years and a PS3 for about 1 (I bought it just after my roommate moved out who had one, so I have been playing for 3 years)
Here are my personal opinions for each, I'll be listing mainly pros:
PS3:
Great exclusives and awesome indie games on the PSN.
The Netflix interface is better (Was better on the 360 until the last dash update when they removed viewing the movies with friends over Live)
Some of the games that were timed exclusive on the 360, when ported to the PS3 included the paid DLC for free or had bonus content added, including some JRPGs and Mass Effect 2.
Blu Ray drive - I haven't actually watched any Blu Ray movies on it yet, since I stream movies from video services, so it depends on you.
No need to change discs: This never bothered me, but since I bought Mass Effect 3 on the 360 it's a little anoying. For Mass Effect 3 they put some sidequests on one disc and some on the other, so I have had to switch the 2 discs about four times now. This hasn't been a problem with any other multi disc game I have played on the 360.
PSN Updates - These can take a long time, so my recomendation is when you find out one came out, set it to download while your sleeping or before you go to work.
360:
Also has great exclusives, most of them older. And some cool Xbox live games
Many of the older multi console games work better on the 360
If your on a budget, you can often get older games for cheaper on the 360 (in the USA, not sure about Sweeden)
Though many disagree, I like the current 360 dashboard and like it a lot better than the PS3 one, but this is not really that important.
I think the XBox Live sevice is better than the PSN, but you pay for it. So depends on what you want.
Installing games: This takes about 20-40min. You don't need to do this, but it cuts down on load times for many games. Do it while having a meal or while your at work.
Final thought: Look at the games that you are most interested in. Also look to see how the multi console games you are interested in play on each. You may consider how many of your friends that you like to game with have one or the other, so you can play with them online. If your on a budget, you will probably be playing less for older games on the Xbox, but you will need to pay a yearly fee if you want to play games or stream media online.
Hope this helps.
