Update: As of SMS Popup v1.0.2 there is now a quick toggle feature for Quick Reply
You can even choose both if you like to have them both accessible easily from the popup - and as an additional tip, if you long-press on the popup you can always access all options (both reply types, delete, view contact, text-to-speech etc.).
Remember to always check the SMS Popup FAQ for tips and tricks like this if you run into problems.
Quick Reply in action: