We went with Surefalp and very pleased we did
We have no electicity in the back of the house where the catflap is so battery power was our no. 1 concern, but the flap works perfectly for all our 8 (9 including Tufty) cats.
Can't fault it - make sure you get the newest model which has a quiet closure - the older ones have a clunky click that spooks some cats.For that reason alone I suggest you buy direct from Sureflap as Amazon and Zooplus may still have the old version in stock.
One thing to note = microchip cat flaps work so long as the chip is in "sight" of the reader. We have one old boy whose chip has now slipped down below his shoulder blade, and the top-of-the-range Sureflap Dual (IN and OUT control) - which has (physically) a shorter sensor for exiting cats - would not read his chip on exit - hence some toileting issues ensued.
However, 8 out of 9 cats did use it successfully, so I really cannot complain. Also their customer service has been excellent.
So if you think you will need to control exit as well as entry, Sureflap are the only company to offer this. Their standard (IN control) flap however has been a steadfastly reliable asset for us, and even with 9 cats coming and going freely, we only have to replace the 4 AA batteries every 6 months.