I'd go for F-Secure. I've seen Trend Micro crumble on day zero threats that F-Secure has gotten.I don't know how to choose between F-Secure and Trend Micro which are light and work well for me.
I believe F-Secure is better but IMO both are mid tier AV's there are better options that are still light. Then again though its your choice and as you've said they work for you.I thought the two were equivalent in terms of protection