I have both and I say get them both. It depends on where you plan to fly. The 4D Lite is excellent for indoor and small areas outside with lite wind. The Yak 54F is much heavier so indoor flight could be tricky depending on the how much room you have inside. The 4D Lite is more durable than the Yak54F and can take allot more punishment. [link=http://www.my89blacksc.com/4dlite2.wmv]4D Lite[/link] Here's a small video of my son flying in back yard. Also Tufflight offers great support by email and in these forums. I would email them if you buy one to ask for any improvements they have come up with since your kit was made. There is a little more building involved with the 4D Lite and you get to express yourself artistically with your own panit scheme I think you'll be happy with a 4D Lite. Also an excellent flying plane with out the worry of destroying it when crashing, repairs if need can be done easy with a little CA and kicker.
Jim