The (long) story on the #4.
Bill Tindall, E.Tn.
When we had the lumber business I had a wholesale account where I could buy Hock and LN tools, 50 and 33% off list. Experimenting became cheaper for me than most.
During a visit to College of Redwoods I saw that I was going to need to learn to plane and chisel to be able to fit parts at the quality I wanted. This started a plane odyssey that largely ended with my "go-to" #5 repaired Stanley Bed Rock, and wasted a bunch of time and money along the way as I grasped at this plane and that trying to overcome my lack of planing experience. I would have to say that I arrived at a moderately successful state in spite of the Hand Tool Forum and other conflicting advice.
Advice to the on-lookers......Buy any Stanley style #4 and a #5. Learn to sharpen and set the cap iron (AKA misnamed "chip breaker"). The shorter length of a #4 may be necessary at times, even if you prefer, or don't, the ergonomics of the #5. Once proficient, expand plane collection to meet personal needs and desires.
Back to the story of the #4.....Following visit to College of Redwoods I built several Krenov style planes. They work, but tried my patience diddling with them. The stability of metal and convenience of screw adjusters made Stanley a lot of business from practical builders for good reason.
Then I bought a LN 4 1/2 with a high angle frog that was to "solve" my tear-out issues. It will appear for sale soon. It was like pushing a boat anchor around, but it was effective for planing surfaces, something I decided sand paper was better for.
Bed Rocks were extolled by the Hand Toolers but they were expensive at the time (not so any longer). I bought one needing a handle and flattening, and I bought the LN #4. Neither solved my tear-out issues, at the time, but they worked well enough that I used them for fitting parts. I came to prefer the light weight and balance of the #5.
As I saw Stanley #4's and 5's in good shape for a good price (less than $35) I bought a few with anticipation I would give them or sell them to those needing an entry level plane, like a son in law.
Plane Epiphany! I discovered Kato and Kawai and the "cap iron effect", followed by Kees seminal video showing that it was easy to set a cap iron to mitigate tear-out. When my stomach was no longer in knots fearing an irreparable divot would be removed while planing, my use of my plane collection ballooned. I soon gained the experience of what I needed for what I did and how I did it, namely mostly part fitting.
I bought a $300 Norris plane to see if it was so wonderful that I would eschew sand paper for refining surfaces like table tops. I sold it an bought another pack of hook and loop for the ROS.
I have my go-to #5 Bedrock preferred for it lightness and good "feel", set with a tight cap iron and fine shaving. It planes anything almost regardless of grain orientation. A #4 LN and a Stanley #3 supplement when a shorter plane is needed. A Stanley #5 is set up as a scrub plane for taking twist out of panels and other fast stock removal tasks. And another #5 is set up for a heavier shaving than the Bed Rock.
Bottom line advice. Any plane will work for most planing tasks once you learn to set it up. Any Stanley #4 or 5 will accomplish most of one's planing needs once sharpening and setting the cap iron is mastered. These planes are now readily available for $25-$35, Bed Rocks for less than $150. I just sold a mint Bedrock #4 for $130 that exactly duplicated the LN #4 and was happy to get this much. Learn to sharpen and set the cap iron on one of these planes. After gaining experience buy other planes to meet your personal needs. I would like to have a LV plane but I can't justify the expense for I doubt it will do anything better than what I have. But the allure of a state of the art new plane is strong.
Fine Woodworking should travel to your shop and do a feature on jigs.