Hi maly2zajac,
PC3L and PC3:
- PC3L uses around 1.35V and PC3 uses around 1.50V (0.15 difference)
- The PC3 will increase a little power consumption and heat.
Points to note:
- It is suggested to use a same RAM Configuration as it is Pre-Installed on your system to avoid risk.
- Their is no such difference except that of voltage.
It is better to have a second opinion: I suggest you to consult with your local hardware specialist to solve your doubt.