Retuning or restringing any axe can make it a new instrument. So many new hand positions and techniques to learn! So many new patterns and combinations to explore! As a guitarist, I'm used to linear tuning, with fat strings on the bottom and thin strings on top. I've adapted to the 'uke's re-entrant tuning. As a fingerpicker, my new Kala 6-string tenor 'uke twisted my mind around -- tuned G4, C4-C3, E4, A4-A3, its lowest string is on top and mostly masks its highest string unless one flips the course and picks near the bridge. I'm learning to pick bass lines with my freshly-calloused index finger. It's just another 'uke, sure -- but the stringing makes it a rather different experience.
I like string tricks. A simple one: tune a guitar in straight fourths to 'rationalize' the fretboard. Chords will be tougher but melodies may be easier. (I did this with a soprano uke. Interesting and challenging.) Almost as easy (except for the calculations): restring a guitar so it's tuned in straight fifths like a big mandolin. Chords will be simpler, and different, and the tonal range with expand. And of course open and modal tunings are there to explore.
A little more work: redo a 12-string guitar which now has the bottom two and top two courses doubled in unison, and the middle two doubled in octaves, so they're ALL in octaves! That will make the bass brighter and lighter and the treble richer and darker. Similarly with a mandolin: set some or all the courses in octaves. It'll play differently depending on whether the high or low string in each course is on top or bottom. Yes, another easy experiment! And for strange, tune the strings in some or all courses to seconds or minor thirds or fourths. I sometimes tune a 12-string guitar ED, AG, D, G, B, ED. Very jangly!
I'm just about to restring a short-neck (21-inch scale) 12-string for fifths-tuning. This is like an audition to see if I want to spend a non-trivial amount of cash on a cittern. A cittern would cost something like US$1000 while the strings will be about US$10. I think I can afford that.
The simplest and cheapest 'uke tricks besides slacking the A to G are 1) go low-G (play more like a guitar), 2) take all strings up a whole tone from G, C, E, A to A, D, F#, B (the brighter 'English' tuning), and 3) the all-fourths I mentioned above, to G, C, F, A# (using the same chord forms as the bottom four guitar strings). Or get tricky: set an 'uke in DESCENDING re-entrant tuning: G4, C4, E3, A3. That will sure mess with your expectations!
Are any instruments or tunings 'better' than others? That depends on how well they're played, right?