A wealth of information concerning Coupon Eligible Converter Boxes (CECBs) may be found here:
The best models with event timers that change the converter box channels for recording to a time-shifting device are the Zinwell models. The earliest ZAT-970A models (where the four underlined digits in the serial number are under 0830) have an undocumented program guide accessible with a $1 remote sold at Dollar Tree.
The best overall performance may be found with the Zenith/Insignia twins, but they do not have event timers and only provide a now/next program guide.
Extended program guides are provided by a few models including the Dish Network CECBs (DTVPal and its variants). Dish Network CECB event timers are, for the most part, non-functional. There are more than 2,000 AVS Forum posts that describe the grief of Dish Network CECB ownership.
I have purchased six Zenith DTT901 models, two Zenith DTT900 models and two Zinwell ZAT-970A models on behalf of my immediate and extended family.