It has been really nice having the two 79-004’s being identical which makes it great for holding long items at the same height.
Yes, I will definitely keep two that are the same height. As of a year ago, that was my Type 4 with steel H-frame, owned since new, and a near-mint Type 2. However, I now have a second Type 2 and another Type 4 with aluminum H-frame that are also that same height.
The two Type 4's make a great pair historically because they were made four months apart and are identical in all components except for the H-frame. The all-steel one is a sentimental favorite because it's my original, and it was a gift from my girlfriend (still together). However, the one with the aluminum H-frame is from the last month or so of production of 79-001's with that iconic feature. In fact, it's currently the final aluminum 79-001 by date that I have documented. I expect to eventually find some that displace it from that position, but it's a fun distinction to have right now.
The two Type 2's are also a nice pair because they demonstrate early and middle production for that Type, differing in four components. The mint-condition one has the current distinction of being the first one among my 160-or-so documented production codes to have the 3-rib step. The other Type 2 is also in very good condition, and has some of the unusual early features that differentiate it from all the others, such as the 4-corner hole pattern and the cone-shaped feet. (As you can see, I'm thinking like a documentarian now.)
Functionally these four are pretty close, including being the same height. The all-plastic vise arms are potentially a weak point for the Type 4's, but I've owned my original for 42 years without breaking a handle or arm, so it doesn't worry me too much. The Type 4's have the additional 1.5" of jaw opening compared to the Type 2's, but I don't really know how often, if ever, I've used that ability over the decades of ownership.
The Type 4's are slightly less adjustable at their full height, due to three slip-on feet on the legs, vs. four screw-in feet for the Type 2's. That could make it harder to get the Type 4's to match each other (or to match one of the Type 2's) exactly on an uneven surface. I wonder if I'll ever need that amount of precision in leveling however.
The weights of the four differ pretty significantly. The heaviest is the early Type 2 and the lightest is the early Type 4, differing by over four pounds. The extra weight of the heavy one is quite noticeable, and I don't like carrying it up and down the basement stairs, for example.
And then there's the Type E and the Irish-made blue Type 3 that would also be hard to give up. I don't really want to keep all six of these, but choosing is hard.