Affiliate Marketing Secrets

What are the pros and cons besides the pricing of $99 per month vs. free? Does Zen Cart have support? I feel I need phone support which is an additional fee with 1Shopping Cart. I will be selling downloadable info products. I also need to track affiliates and pay their commissions. The autoresponder is also important. I am concerned about starting with one and losing opted in prospects if I have to switch over. Does anyone have experience with both?