I have the Mayer RM58, and the 615 Limiter/Compressor. I use them in my guitar chain, and they are wonderful. I love them better than any others out there.
While some say they can be noisy, I haven't had that problem with my EHX Blackfinger. I did put 2 x NOS Mullard l61s in it, but unless its dimed, which I don't do, its very quiet.
I like o run the EHX into 1 of the Mayers, tube, into Solid State, but you have to be careful not to run them to hot, or you will get noise, but are great if dialed in correctly.
I would guess the Effectrode is probably a better pedal than the EHX, but Ive had the Blackfinger since 2004, and its served me well.
But IMHO its hard to beat either the RM58, or the 615.
615 is Highly Recommended for the $$$. Has a 10Hz-100KHz Frequency Response, and is also Optimized for Digital, with Feedforward Design. Cornish also uses this design.
615/RM58 runs either Line Level, or Instrument Level.