The classic loop is quite different, like the MP2 it has a stereo parallel loop so you can program the return mix level to mix in FX with the dry signal, with the parallel loops (Classic and MP2) it's best to run the effect at full wet and use the return mix level to balance with the dry signal.
The MP1 loop is mono and serial as in the effect is inserted into the dry signal path and you need to control the mix balance (dry/effect) with the effect's mix setting(s) (and tweak the effect input and output levels to balance with the loop send/return level knob). The classic and MP2 loops are much better for lots of reasons. Some of the Classic's "enhanced" features (eg stereo parallel loop, cab simulated outs etc) were precursors to the MP2's feature set. I didn't see Classics in Australia, I went from MP1 straight to MP2 when they were released here.
As I said previously, some like the MP1 loop and get it sorted, some don't like it and patch FX in other ways, the most common is probably MP1 A/B out > FX L/R in, FX L/R out > power amp L/R in. (dubbed the 4 cable method (4CM)).