I haven't tried the Microphone Cassette, but I do have a Portico II Channel, a pair of TG2s, and a Curvebender (as well as some of the Chandler Tube Gear.
I'd say, if you don't need a higher channel count, it would be nice to have the Chandler feel. The TG series stuff is very good on guitar in particular, imo, but it's also cool on all sources I've tried it on.
The Portico II is, however, one of my most often used pieces of equipment because it just has a lot of handy features, like the De-Esser, HPF, DI, Line In, Parallel Comp, etc. It's maybe not my favorite EQ, ever, but it's also no slouch.
The Chandler stuff is is definitely more about a "vibe" and would expand the range of sounds you can get.
Of course, if you are tracking drums, maybe the increased track count of Portico II would be handy as well.