Yamaha LJX and FJX

I don't know much but the L series is a little better quality then the F series.  L is more like a upper mid grade, were I think the F series is slightly lower in quality of materials.  Yamaha makes very very good instruments and I don't want you to think I'm saying its a lower quality guitar because the craftsman ship on every yamaha I have ever picked up was fantastic.  I own a very cheap FS720S $300 and with a tusq nut, bridge, and bridge pins I installed I've had people with C.F. Martin OOO-18's say for the money its not a martin but its very close in sound.  Thats compairing a $2000 guitar to a $300 guitar, its not apples to apples but for the money its amazing how close they really are.  Back to the L series I believe the biggest difference is electronic pre amps.  That would be my guess.

I really believe that as far as an acoustic sound both will sound very much the same, You will find one has a better pre amp then the other and I strongly suggest you play both through an amp before you take my word on anything.  I have never played either guitar but I am a huge fan of yamahas ( I've owned 3 acoustics and 2 electric guitars that would have stood apples to apples with any american made guitar) I looked up both guitars and gave you my opinion with what I know about the guitars, and my experience with EVERY Yamaha instrument I've came in contact with cheap or high end.  The lowest end would have to be my old Gut guitar I sold recently.  It was not a red label but it was from the 70's while I could keep it in tune it had the most beautiful sounds I've ever heard from a Gut guitar that I've played.  I sold it for $100 on ebay and the man that bought the guitar couldn't put the thing down.  It was a cheap guitar for his son that ended up being a very nice piece that he kept himself and bought another cheap guitar for his son.  Another great experience was my AES620 single cutaway guitar.  They were like $500 or $600 new when I bought it blue flame top that reminded me of a blue M&M because the back was chocolate brown and a natural maple unstained line where on a les paul you would have binding.  cracked that one out many jams because it had this natural Jimmy Page tone without using a bunch of pedals to get there.  Opened it up and the body was completely sheilded with the sheilding paint.  Not some sorry job gibson usa does but a very thick coat that had no thin spots.  That was my rock 'n roll guitar but it was cheap compaired to my RGX-TT Ty Tabor signature model.  That guitar too had a nice Led Zeppelin growl to it.  Both had a Seymour Duncan JB pickup in the bridge so I guess that was my favorite pickup, but when I put one in my Les Paul Classic I hated it.

Long story short you do get what you pay for from Yamaha, and even though I think both guitars are going to sound great if you think your going to play out I would suggest going for the better preamp.  Let the ears do the talking not some guy on a forum because if you can hear a difference then you owe it to yourself to get what you like.

Well the good thing is now days a good reputable store should have a return policy so you can return anything you don't like such as an online store.  If you can handle the extra expence try ordering both and return the one you don't like.  Here in the states I've used Musicians Friend they have a 45 day return policy no questions asked.