I just completed Mass Effect 3 for the second time. The first time, I imported my ME2 character... but I decided to start off a new character for the second time around without the character import to see how much of a difference it would make.
I can give you a rough draft comparison of my two games:
- Started at level 20+ with Import, but at level 1 without it
- Cerberus is suppose to be more powerful if you let them have collector's base in ME2 but I couldn't tell a difference
- Your ME2 Squad Members will appear (mostly cameo appearances) if you do an import
- Garrus, Tali, Joker, The Doctor, Liara, appear and become part of your new crew.. Legion makes appearance
- Jack, Zaeed, Miranda, Samara, and Thane will make an appearance if you imported them over from ME2, otherwise they don't exist in ME3 (except Miranda.. she will make cameo apperance). Also they will save an important person at "Key Moments" in the game.. If they're not there, the person just ends up dying... won't affect game...so don't worry.
- Any of your Squad Members who died from ME2 suicide mission will not be there... Miranda was the only one who died on my ME2 game, so she didn't appear when I imported over my character.. but she did appear when I didn't do the import...
- Another thing to note... Kelly Chambers died in my ME2 Game... but she appeared with my character import, which shocked the heck out of me... But when I did NOT do the import, she didn't exist with that Shepard... so she seems to only appear if you do the import... and it makes no difference about her dying in the suicide mission.
As far as Renegade and Paragon points go... this is not much of an issue with ME3. There are only like 1 or 2 instances in which you're given the special dialog... and they don't really matter...
So from what I can tell... you will have MORE skill points to use if you do the character import... without the import, my character was only able to go from Level 1 to Level 40. With the character import, my Shepard was about 10 levels higher (Level 50).