I was using the Boss RC1 until I decided to get a BeatBuddy to lay down my drum track - came up against the dreaded clock sync issue - the cheaper loop pedals don’t have MIDI sync capability so when you start overdubbing everything quickly goes to sh*#. Ditto x4 appears to be the cheapest option in hardware with MIDI, although Loopy on my iPhone is also an option with something like the IK Multimedia iRig Stomp guitar interface and a BlueBoard for foot control.