I like the early Millers Falls planes. Their fit and finish was excellent. They have a two piece hinged lever cap that spreads pressure on the cutting iron / chip breaker assembly over a broader area in order to reduce blade chatter. The idea is that it is less likely to flex the thin blade, pulling it away from the frog at it's mid point. I think it works fine, but does tend to require a tighter setting to keep the blade from shifting. This means adjusting the blade depth requires a bit more oomph. That, in turn, stresses the adjustment yoke, which is why Millers Falls moved from a cast iron yoke (earliest versions of the plane) to the steel yoke that was most common. It's not brittle and likely to crack under stress.
The later Millers Falls versions got away from the hinged two piece lever cap. These planes were lower quality than the earlier ones - about on par with cheaper Stanley knock off's. Serviceable when tuned, but definitely not worth much money.
The Stanley #5 may be a good plane, depending on its vintage. Most users shy away from hand planes made in the last half of the 20th century. Power tools were flooding the market. To compete for market share, hand tool makers aimed at low price (and cheap tools) instead of performance and quality. Parts became flimsier, made with poorer quality materials, and machined to lesser standards. Stanley was no exception. For detailed information on how to date a plane, google "Patrick's blood and gore" at the "supertool" website. It's a great resource and full of useful information for someone who's somewhat obsessive and doing homework on hand planes.
My favorite old planes are Record (Stay Set versions), Stanley, Millers Falls (hinged lever cap versions), and Keen Kutter (single "K" versions) from pre-WWII. For minimal investment and a couple evenings of time / effort, these can be finely tuned and easily adjusted. Stanley Bedrock planes also have a cultic following. The basis of the design is to secure the frog more securely to the sole casting in another effort to minimize chatter. The configuration has been copied by several current plane makers (Lie Nielsen, Wood River, and Clifton to name a few). The Keen Kutter (single "K") planes are the same. The Bedrock planes work well, but you'll pay a stiff premium for a small performance improvement. Unless you're a well seasoned plane user, you'll likely not even notice the benefit.
The older totes also tend to fit my hand better than the newer ones. That's no small thing when you're looking at a long planing session.
Have fun with it.
paulh