Hello Hou_ge2000,
Welcome to the Forum. Your question above generates many other questions before any one of us can truly answer you. The first question being: Which Tamiya tank are you thinking about buying? They are very different, with each one possessing different advantages and disadvantages. I can begin by telling you about my Tiger I. It's an excellent model for many reasons: Definitely worth the money, seriously fun, very impressive and realistic. Tamiya did it's homework well. The Tiger I also has a great deal of aftermarket products out there available. (Probably the most for any of Tamiya's R/C tanks.) The Tiger I and King Tiger have very realistic sounds and movements. Now for the disavantages for the Tiger I: Although it has adjustable tension for the tracks, this does little when you're running the tank in soil with small rocks. These rocks can jam your tracks and either pop the track off or worse, lock up your gearbox and strip it. This can be fixed if you rig up spring loaded idler wheels. These will aloow for some give and take in the tracks. (Incidentally, I recently took my Tiger to compete in Danville, VA and kept my tracks a little loose. This worked out very well and I had no problems.) The majority of the Tiger I kits out there now have the older, Type 1 gear boxes. They run too fast for true scale Tiger I speed, and the stock electric motors are horrible. If you get these, do yourself a favor and buy the Type 4 gearboxes (King Tiger gearboxes) and two 6 volt Graupner 400 motors. Rumor has it that Tamiya will be discontinuing the Tiger I, so if this is your choice, snatch one up now. Tamiya makes two WWII German tanks and two WWII US tanks. The US tanks are the Pershing and the Sherman. From what I've seen, I'd buy a Sherman. They are easier to build and there are many different aftermarket conversion parts and extras available for it. Plus, the Sherman gives you more room in the kit to work with. (The Pershing crams a lot of gear in a VERY small space. Check out the various armor websites of folks here that have built and run them: www.fragarmor.org , www.MAADHQ.com , www.rcarmorforum.org ... to name a few. Also check out the 1/16 Tiger I build sticky here in the forum to see the trials we encountered building the Tiger I.
Good luck and keep us posted as to what you do,
Okieboy