Open Source CRM Comparison

I would like to choose an ideal CRM for a client. It must be open source. But I don't know CRM systems. I'm starting discover world of CRM systems by this post.

1. Zurmo

Pro:
Awesome design and user interface
Fast ajax and Yii in use
You can configure data structures (contact, company, task, meeting). You can extend anything with custom fields.

Con:
Very young CRM with actually smaller community than other CRMs
Some feature is missing: E-mail marketing, Google Calendar integration, etc.

2. vTiger

Pro:
It has experience.

Con:
Ugly design...
Too complicated
Too much feature for a small company