Hi Mike,
MC5 and SHS7 (and the SHS7XL version) are very similar in looks and functionality. the only difference between them is that SHS has more functions available including sysx send/receive, custom INS DEF, I/O limits, bus and FX limits and track limits.

MC5 is limited to 8 buses, 8 softsynths, 8 FX per track, 24 FX per project, 2 simulaneous audio inputs and outputs, 32 audio track limit per project and 128 MIDI track limit per project. SHS's limits are much higher on all counts and the I/O is limited only by the hardware.

the XL version comes with more softsynths and FX.