The DeArmond M75 is a well built guitar with the feel of a Guild with a little chunkier neck. The neck block inlays are not as aesthetical as the Guild or NS models. They are heavier. The M75 has Goldtone Humbuckers and they they have a clean bright tone for a humbuckers. The M75T is also a good quality guitar using DeA Model 2k single coils that are more like a lower output P90. They are not the same as the model 2000 single coil which mimics a lower output vintage 2000 pickup.
The DeA M77 is similar to the M75 except it has a hard stop instead of the floating harp stop. It is also about 1/8 inch thinner. Subtle difference in headstock shape and size, tuner "buttons", TRC and color options. I especially liked the M77T and wish I never sold mine. The M70 is a slab body with many similarities to the DeA M75 but less fancy hardware, no neck binding and it has the same hard stop shape as your Guild M75. The M72 is another flat slab type model but it has a maple cap, neck binding, dot fret markers and a combination of gold and chrome hardware. The M72 is a good looking guitar. The non "T" models all have the Goldtone Humbuckers. DeA guitars made in Korea are the higher quality models. M and S models with model numbers in the 50's and 60's are the cheaper grade and 70 the higher grade (M50, M55, M65, M68, S65, S67) vs (M70, M72, M75, M75T, M77T, M77T, S73, S7312). All the hollow and semi hollow archtop were good quality and the Jetstar, 7-Star, Bajo-Jet are high quality with Jet Star Special being of lower grade parts and finish.
Similar scenario for the bass guitars. Essentially back in the late 1990's the Indonesian made guitars were of lower quality than Korean. Now they are approaching parity.
When Fender started to consider selling Guild they purged the Dearmond line first and they were available at blowout prices. Today the NS are in the same price range as the escalated DeA so a good value is available at a reasonable price.