TH115 AF vs Tekmar 519

Hi, group! Installing suspended tube floor radiant upgrade in a sun room. Concerned that significant solar gains will overheat the room, but cutting the floor heat off entirely will leave it too cool to catch up at sunset. Looks to me like these thermostats will maintain a minimum floor heat even after the ambient T is satisfied. I am really impressed with the features on the Honeywell TH115 AF 024T and the Tekmar 519. I read about the Tekmar first, and it seems like exactly what I want; then saw the Honeywell which seems to be very similar, but includes 7-day program. I prefer the smaller simpler display on the Tekmar, but with the Honeywell running $23 less it seems like the better choice. Perhaps the Tekmar is higher cuz their probe is designed for slab immersion, while the Honeywell is just everyday. There is a big difference in the probe prices when sold separately. T'stat will go to a TACO SVC404-4 to control a Taco Z075T-2 zone valve. Anybody have a hands on comparison between the 2? Any opinions based on brand name? PS no A/C in the house. just oil-fired hot water radiators.