We do not consider other options for large companies but do install FortiADC for small to mid-sized companies. 

We evaluated Imperva, but F5 Advanced WAF was able to outperform Imperva.

We tend to stay with F5, however, we will look at pricing and try to negotiate based on that. We'd like to get a discount and look at the market to see the costs. 

Our clients pick this solution over others because it is one of the leading companies in the category.

I reviewed Imperva only to compare pricing.

Before selecting this solution, we looked at Kemp. We were concerned with the WAF, which is why we decided not to go with Kemp.

I evaluated a few other options. Kemp, for example, but Kemp is not a WAF it's a load balancer, it's for another model of the F5 so its not related to do WAF. And we're speaking about the WAF. 

We are constantly looking out for features which are not available in the current product. We have set alerts to flag when these features become available.

I evaluated FortiWeb.

We chose this product because we believe it is the best product for us. There are other firewalls in the market, but you always look for the best as a vendor.