The screens on X32 and X61 should be comparable. I never found neither of them too dark, although in bright sun they won't be very usable.
When traveling, I assume you run your laptop on battery? Make sure to go into the BIOS and set the LCD brightness from "Normal" to "High". This will make sure it will be as bright on battery as on AC (a big difference in usability, IMO, although of course you pay with some battery life).
It is always possible that your particular screen has something wrong with it - maybe a worn out backlight that lost a significant portion of its brightness; hard to say without looking at it side by side with something else.
Comparing the X32 to T43, they are quite similar. They start at about the same performance level for the low-end configurations (1.6GHz CPUs), but the high-end T43s go higher (up to 2.26GHz, whereas the X32 max is 2GHz). T43 RAM is also faster (DDR2-533 vs DDR-333).
Current: X220 4291-4BG, T410 2537-R46, T60 1952-F76, T60 2007-QPG, T42 2373-F7G, X61 7673-V2V
Collectibles: X32 w/ IPS Screen, A31p w/ Ultrabay Numpad
Past: Z61t 9440-A23, T60 2623-D3U, X32 2884-M5U