I dont have chanel vintage mini, but i do have chanel mini rectangle and gucci marmont mini flap.. i love both!! You can put more stuff in Gucci mini marmont flap than chanel mini rectangle because the leather is so much softer.
i have two vintage minis and they'll stay in my collection forever. they are amazing quality. the specs tend do be varied though, the vintage minis were less standard than they are now, so pay attention to chain length, depth, and length, which seems to vary a lot with the older mini bags. i like the look of gucci marmont and like gucci leather overall, but would never choose a gucci mini over a chanel one. the marmont print isn't timeless, perhaps if the gucci mini was just plain black it might compare.