BenQ RL2755HM Official Gaming LED-Lit Monitor $299.99 @Amazon
Resolution (max.) 1920 x 1080
Input Connector D-sub / DVI/ HDMI
Panel Type TN
BenQ XL2430T $379.99 @ Amazon
Resolution (max.) 1920 x 1080
144Hz refresh rate
Input/Output Connector D-sub / DVI-DL /
HDMI 1.4 x2 /
DP1.2 / Mic in /
Headphone jack /
Mic jack
Panel Type TN
OK, your links were to Amazon. I used their prices here.
The differences are a few. Both monitors are 1920x 1080, but the cheaper one does not list a Hz frequency on its stat sheet, which means it is a 60Hz monitor like nearly all monitors are. It has 3 different connectors. Amazon only lists "Low Input Lag; Dual HDMI", but I think I would go with what the BenQ website says, which is "D-sub / DVI/ HDMI"
Now the more expensive monitor... It also is 1920x1080 resolution ... BUT ... at 144Hz. In other words, this monitor can refresh 144 times a second vs the 60 times a second the first one can do. Here is the facts on this. 144 frames per second means your video card has to generate 240% the number of frames a 60 Hz monitor needs. Most video cards are having enough trouble maintaining 60 FPS right now, and I can only imagine what trying to pull 144 FPS out of those cards is going to look like.
On to connections. Input/Output Connector D-sub / DVI-DL / HDMI 1.4 x2 / DP1.2 / Mic in... I believe DisplayPort and HDMI are the future. DVI-DL might be able to handle 144 Hz, but I am not certain of that. And then there is a headphone jack, and a mic jack. I do not know how useful these are but some people want them, so here they are.
I do not know what kind of CPU or GPU you have. If you have something that is not top of the line or very close to it, I would suggest going with the cheaper monitor. But if you have a monster system with a couple Titan X's, or a pair of R9 290X's, or even a couple GTX 980's or GTX 970's, well, then the more expensive one might be a viable choice for you.
And finally, one last point. Both monitors have regular TN panels. I prefer IPS panels. IPS panel monitors have really come down price-wise in the last few years. This is not a deal breaker. TN has come a long ways over the years. But so has IPS. And the price premium for IPS is minor in most cases now. At the very least look for one that's comparable, and see what you think.