That's probably an oversimplification.
The 688 and 488(std/mkII) each record 8 tracks onto cassette.
The 688 records 8/simul, and the 488(std/mkII) records 4/simul.
The 688 has 10 full mixer channels, and the 488(std/mkII) has 8.
The 688 has 20 total inputs, and the 488(std/mkII) has 12.
The 688 has 8 subgroups, and the 488(std/mkII) has 4.
The 688 has 10 XLR mic inputs with 10 preamps, and:
... the 488(std) has no XLR's and 2 preamps;
... the 488mkII has 2 XLR's and 4 preamps.
The 688 has inserts on all 10 channels, and the 488(std/mkII) has 2 inserts on the first 2 channels.
The 688 has 8 Pgm-Outs, and the 488(std/mkII) has 4.
The 688 has 8 Tape-Outs, and the 488(std/mkII) has none.
The 688 has fancy electronic routing and switching, and the 488(std/mkII) has standard switches and buttons.
The 688 has 3-band EQ, and:
... the 488(std) has 2-band EQ;
... the 488mkII has 3-band EQ that's equivalent to the 688.
The 688 has an LCD control/routing display with a large LED VU meter bridge, and:
... the 488(std) has a simple black & white LCD VU display.
... the 488mkII has a highly visible Flouro-Luminescent VU meter display.
...
...
...
Other than that, they're identical!