I have a whole desk full of calculators. The two I use most are:

Sharp EL-W516X A very capable little dot-matrix device, with some limited programming / macro ability. Performs all of the calculus, stats, matrix, and combinatorics functions I use regularly. This was my go-to calculator until I started using the…

Casio fx-115ES PLUS At some point, I had to write some exams which only allowed a few calculators off an approved list. This was the one I picked from the list. It is a very competent little device which can do anything the Sharp unit above can. After getting over the novelty of having to learn a new keypad, I found it nearly identical to the Sharp in usage.

I think that both calculators are effectively identical in terms of function, but the Sharp may have a slight advantage in terms of its interface. I would wager it takes slightly fewer keystrokes for the same operation on average as compared to the Casio. I also didn’t really take advantage of the programmable aspect, instead using the four keys for the common multipliers I use in my work: kilo, milli, micro, nano. I liked how the display would read in “natural” terms like “2 * pi * 10k * 100μ” instead of having a tonne of “10^n” terms in the line.

The Casio has the advantage that it is typically on just about any approved calculator list; if you’re taking exams down the line, consider getting used to an approved calculator now so you’re not wasting time searching for buttons later. It’s also the more popular choice, I think. I saw plenty of students, TAs, and instructors using this calculator which could make it easier to give and receive help on it.

Casio FX 992 always seemed very ergonomic and easy to use, although it might be considered a bit vintage now. It had a sheet of physical constants, so for example 90->const enters the speed of the universe in m/s. Having a random number generator built in can be quite convenient sometimes.