Hi there,
In a nutshell...
The LF347 offers several advantages over the LM324, but it does have it's problems too though.
The LF347 has at least twice the bandwidth of the LM324, requires 1000 times less input bias current (higher input impedance), slew rate 10 to 20 times faster, among other things.
Despite it's advantages over the LM324, the LF347 does have some serious drawbacks that limit it in applications that have rather low supply voltages. One of these is the input common mode voltage range, which means the input may not be able to go to within 4v of either supply rail. In contrast, the LM324 can work with an input down to 0v and up near the positive rail less about 1.5v, which isnt too bad. This one problem alone means it may not be able to work with a single 5v power supply used in many projects today.
Also, it requires more power supply current than the LM324, about 10 times more.
In short, the LF347 is an older design FET op amp and really requires power supplies that were common many years ago like plus and minus 15 volts, or at least plus and minus 10 volts.
With a supply of only plus and minus 5v for example you may find that your input signal has to be limited to plus and minus 1v because of the input common mode range limitation.