Having a clear idea of what you want from what you're building will probably help, regardless of what platform you end up using: generally blog posts for things that are located in time (events, diary/news items) and pages for the more static stuff (about, contact, team pages, project indexes, things that keep the same relevance as time passes...)
Regarding the two personae: wordpress.org requires you to have your own server access, and you can tweak things a lot more as a result. Wordpress.com sits on their servers, you can customise things less but can still change theme options and how you organise the content on your site. Have a play with a wordpress.com site set to private whilst you figure out structure, content and your voice.
I started using it around 2004 sort of time and have had no reason to move away. I use it for my own projects, short-term schools projects, documenting commissions etc. I like how you can always get your content out of it should you choose to relocate. The writing interface is getting more annoying though (there are plug-ins to revert back to the old interface if you're using wordpress.org)
If you're doing e-commerce stuff then it might, er, pay to do your research about how to link different platforms up for money and sales handling.