It depends on what you wan't to do and the money you have. Sure an E3-Flasher is cheaper, but you need to know what you are doing, you will need to open your PS3 and "mod" the hardware. So if you don't have any experience with this kind of stuff, DO NOT rush in things, take your time, read twice the instructions and be careful.
If you have enough money to buy a 3.55 PS3, do it. It's safer.
But then again, It's your choise !