It is not designed as a fine woodworking tool, but designed for fast stock removal by carpenters, with the fine tuning to be done with a rabbet or shoulder plane, the "90" series by Stanley. That being said, you can do precise work with it, but it takes some adjustment and fiddling. One of the reasons a 778 is better is the dual rod fence is more stout, as the 78 fence can have some slop or inaccuracy in it; hence the use for roughing out with the fine tuning being done with other planes.
Stanley made a higher end 78, the 278, check it out in Blood and Gore; then there was the skewed 289, which is pretty much like a 78 but the skewed iron makes for a real nice cutting plane; but the 278 and 289 have fences distinct from the 78 which that are more robust and the hole for the rod is centered, which makes the fence more effective and more capable in my book; I had a 289, but sold it (its not all that common, and collectors love them, they like the 278 even more because of its design and relative scarcity) and bought the Veritas version when it first came out, which as the dual rod fence, is much more user friendly and is a real cadillac of rabbeting planes that IS capable of doing quite fine work.
Now, this is only my experience from using them, others may differ, but that's it in a nutshell. All this being said, I still have a 78 in my user traveling toolbox, and a Record 778, with is superior to the 78 IMHO, principally because of the fence. What I wish it had was the little thumb hold that the Sargent version of the 78 had, some of the Craftsman versions made by Sargent have them too. Anant makes an A78, basically a knockoff of the Record 778, that actually has a front knob affixed to the bullnose section, which I'm thinking of fabricating for my Record. Here's a pic of that below. Highland Hardware used to sell it, but haven't for a while now, don't know if its imported at all to the US.
I'll shut up now, I'm starting to ramble.......