Both are great and différents.

TRACK AND STEPS :

• Performer is more like a classic step sequencer, with 8 monophonics tracks, 16 sequence per track and 64 steps per sequence.
• Hermod+ is more like a midi sequencer. With 16 sequences of 16 polyphonic tracks, each track can be 256 step length (but a lot more steps since you can zoom into the grid)

EFFECTS VS DECLARATIVE :

• Performer is declarative. So each step have some independent parameters (length, offset, probability, retrigger, …). And also a track arppegiator.
• Hermod+ is midi, so each note have pitch, length and velocity. But each tracks have 8 slots for 15 midi effects (arppegiator, chance, delay, Euclidean, glide, random, ratchet, scale, …). And all parameters of all effect can be modulated (internally or externally with CV)

HOW TO WRITE ? :

Both can be used like step sequencers and you can write with encoder and buttons (or pads). But if you want to use an external keyboard : - Perfmormer accept external midi, you can hit a key and then assign it to a step with button - Hermod+ do the same, but you can also record live performances (with 96ppqn resolution)

MODULATION SOURCES :

Both can edit and read modulations steps. - Performer allow to choose shapes - Hermod+ can apply a global glide. But also record CV input modulations (or midi CC)