Plus something using large NAND Flash storage like SD cards beats a device that uses relatively small NOR Flash ROM as you can fit every PCE game you would want to play on a SD card but not likely into the somewhere around 128 megabits that the largest PCE Flash Cart can hold.
I used the Neo Flash Sega Genesis/MD cartridge along with their SD adapter in the past. It was extremely expensive, $200+. It wasn't bad or anything. It included the FM chip for SMS games which some people would like, didn't mean much to me. I ended up selling it and sticking with my ancient Double Pro Fighter until later buying the EverDrive which beats everything else available easily.