1. Protection
2. Throughput
3. Ease of use
4. Support
5. Price
I want to make sure it fits my needs and does what I need to do. Every environment and budget is different. Making sure you talk to people who know what they're doing so you get the product you need.
The Barracuda products are very good and quite pricey, especially since you mentioned you were looking at the Sonicwall TZ series. The Sonicwall TZ series is meant for a smaller environment. The Fortinet firewalls are great but require a little more training. My experience…