One thing that has always befuddled me with HP calcs is their model numbers that don't seem to follow any rhyme or reason. How does the functionality of DM42 compare to for example WP34? And how does -48 compare, besides the relatively useless graphing capability? I see lots of people also preferring some other models (15, 16, 35, 41 etc), which I would have imagined to be strict subsets of these "juggernauts", but maybe that is not the case?

The 48 was quite a bit bigger than the 42s, which I think is the main downside. A bit of googling suggests the 48 contains similar features to the 42s, and probably more. It can also show the full 4 level stack - the 42s showed 2.

However, you're looking for the best all-round scientific calculator (form factor restricted!) the 42s probably wins. The voyager series (including the 15 and 16) were well-made and in landscape format, which is nice for using on-the-go with both thumbs. They are more simplistic though - you see one line of the stack, and there aren't menus - hence several variations to cater for different markets.

The HP41 was an impressive programmable calculator for its time, and seems to be more expandable than the 42s. However, the 42s is programmable, has a few more features and a more modern display.

Not sure about the WP34, though if you look at the cost of a second hand 42s, you'll see that many people rate it much higher than more modern HP calculators. I think what puts me off more recent calculators and even some other HPs, is the ambivalence about RPN. I really like RPN, and don't like when the UI is compromised to please both.

[1] http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv005.cg...

How's the menu interface in HP calcs, is it strictly better than non-menu ones, or is it more of a usability compromise to allow packing more features? In other words, are the non-menu ones better for the subset of features they have?

I'd say the way the menus are implemented in the HP42s is more useable than trying to cram things onto buttons. For example, on the HP12c you have to remember which registers the sum and mean of x and y are - usefully it tells you on the back. The HP42s is more explicit with its soft menus.

> One thing that has always befuddled me with HP calcs is their model numbers that don't seem to follow any rhyme or reason.

Back in the day, HP had nice sales literature that described the differences between the models quite nicely.

> And how does -48 compare, besides the relatively useless graphing capability?

The -42 and -48 were both intended to be successors, of a sort, to the HP-41 family. The -42 It was less expensive than a -48, and placed more emphasis on a function-per-key style of operation, as well as -41 compatibility. (The -42 was program source-code compatible with a nicely loaded instance of a -41.) Where the -42 suffered in comparison to the -41 was that it did not offer any kind of expansion slots, and, unlike the -41, the -42 was never intended to be the 'top of the line'.

To understand the -48, you need to look back to the -28 (as well as a couple of similar business models). After developing the -41, HP realized that they needed a new higher level internal programming model to take the calculator line to where they wanted it to go. In reaction to their growing ambitions, they developed a language for their calculators called RPL... Reverse Polish Lisp. There are a few examples of RPL in this thread, but if you think of a dynamically typed type safe variant of FORTH you wouldn't be far off from RPL. It was RPL that brought features like symbolic algebra, graphics, and a >4 level stack HP's product line, and it was the -28 that was the first scientific instance of this platform. However, the -28 was a bulky clamshell design, behaved fairly differently from a -41, and was sold in parallel with the (still popular) -41 series.

The -48 was a more spiritual successor to both the -41 and the -28. The -48 unified the new programming model of the -28 with the non-folding portrait style casing of the -28. The -48 also added a serial port and a couple expansion ports, so it carried forward some of the -41's legacy of expandability.

> I see lots of people also preferring some other models (15, 16, 35, 41 etc), which I would have imagined to be strict subsets of these "juggernauts", but maybe that is not the case?

I have an -11, a couple -48 variants, and a -42 emulator on my phone. While the -48 is strictly the most powerful, it can also be a bit cumbersome to use. The smaller platforms have their place.

The 48s show you four rows of stack at a time, and can use that to show a single long expression. That can be a huge difference—though of course, unlike the time when these were built, we have Octave and similar right there.

DM-42 seems to also feature multiline display (I'm kinda assuming that it will be showing the stack?), so that advantage is mostly negated there?

I bought an HP50g, new, just a few years ago after my 48 died. I believe that they have a new one called the Prime that's still in production.

My 50g is an excellent machine.

My trusty HP50g which I used in my undergrad was stolen, and it still makes me mad because it's unlikely that whoever took it will take full advantage of it.