Hello! I started with Community Builder. Then changed to Seblod.
A bit of learning curve, but a lot more flexibility in the end.
Seblod is capable to do everything CB can do and much more.
Templating is much easier with Seblod.
Ability to create custom search list easier with Seblod - CB not capable of separate menu items per search list without showing dropdown menu of other lists. [unless you modify the code then watch out for updates].
Importing/Exporting data easier with Seblod or directly from database as you have control of tables with Seblod.
Both Seblod and CB are 'heavy', so if you need tables or other list types for your site, why use 2 extensions?
If you purchased the most popular Seblod plugins which have Lifetime License and Free Updates you spend equal to 1 year subscription of Community Builder. I would start with SD Field Concat, SD Live CCK, Captcha, History Back, and SD Simple Simon template.
Good Luck!!!