Rooting is basically giving you the option to install different roms for a different look and feel to suit your needs (or for fun), possible better batt life, and able to remove the bloatware.
If you root and stay stock, it will be the same as what you have now but with flashing of new rom capabilities and will not lose swype. But if you flash a different rom, it all depends on what the chef cooked into it. You'll have to read on what the rom has. Some might have swype, some not, some might be pure android, some might be touchwiz 3 but with a twist.
Rooting gives you options different to normal users and able to customize at will. Rooting (unless you root and stay stock) can have negative side affects like the dreaded Los (loss of service) that's pretty nasty.
I know on other phones rooting can give you access to free tethering, I'm not sure about the E4GT so I won't comment on this.
All in all, rooting can give you options otherwise not accessible to staying stock. Rooting can also cause problems. So take heed, read, understand, and do what YOU feel is in your best interests. Good luck!