HP-29C - Brighter LEDs?

[rprosperi]

One of my 29C's is indeed a bit brighter than one of my 25C's (these are handy, others are not) but I would not say 'significantly'. (Your OP mentioned the HP-25, it's not clear if you are including -25C's as well).

I'd say you need to have 100 or so mixed results that are very biased towards one model, or no difference, before you could conclude there is a specific trend, or probably well less than that if all answers are the same.