As the lads said, it depends on what you want to do and your budget. Also, for a Tamiya or other kit tank, it also depends on your modelling skills, and what you actually want in a tank. I would recommend 1/16 scale, especially if you want to get in to combat and such. Also, you may want to find a local tank club. There are lots around. Tankers are usually a pretty good bunch, and will set you on the path to build or mod your tank to what you want.

Heng Long tanks are basically a toy tank that has possibilities. Many of the tankers have taken these tanks and done wonders with them, up to and including Tamiya electronics, metal tracks, lots of detail parts, etc. They come basically ready to run, however be advised that they may not be particularly scale in appearence. Wasan RC tanks are the same, although with somewhat better initial quality and scale fidelity. The Wasan T34 does come with a lot of detail parts, and picture instructions as to where the parts go. Use a gel type acc glue to attach the parts on a Wasan. The Wasan will need some serious upgrades in the motive department relatively soon after you buy it. The trans gears are suitable for indoor use generally, and have a clutch in each side which gets weak fast. Both makers, HL and Wasan, use no bushings or bearings in their road wheels or idlers, so if you intend to run the tank outside, be prepared for wear on the wheel system. Plastic on plastic has a finite life. Tamiya uses bushings or bearings in their road wheels, but curiously not in the Sherman idler wheels, which wear fast. There are solutions out there for the Sherm idler, though.

Tamiya is the top of the line in RC tanks. They are considerably more expensive than HL or Wasan, but you get what you pay for. All come with full electronics in the kit unless clearly stated that it is a static model kit. Their most simple tank is the Sherman. Reliable, an easy build out of the box, and a real good runner. Panther/Jagdpanther would be next for ease of construction and operation. Then Tiger 1, a very detailed tank, but again excellent runner OTB, then King Tiger. The Kings idler adjustment system is pretty poor, but with a minimum of fiddling, works OK. Next in degree of difficulty is Pershing. Another good runner, but pretty cramped inside. Then the Leopard 2A6. Fabulous modern tank, stuffed full of electronics, good drive system. I have not built a Tamiya Panzer 4, so can give no judgement on it, but from what I hear, it is also a good runner OTB. For all Tamiya tanks, there are literally scores, if not hundreds. of detail parts, running gear upgrades, transimission systems, tracks, idler systems, etc etc. You can pretty much build most any tank from Tamiya to any time period the particular tank was used. There is also lots of research and info sights for the tanks. Makes for quite interesting reads, and the historical aspect is excellent. Rumor has it another tank is coming from Tamiya very very soon. Have no idea as to what it is.

Do not buy a Heng Long or Wasan tank with plans to upgrade it to full Tamiya or Tamiya type electronics. It is not cost effecient.....at the moment. There are soon coming developements in that vein which will put paid to my statement and open up a whole new world of tanking for HL and Wasan, and older Tamiya static models, and the system will be plug and play. More on that before the year's end, I think. First, and this is a given, a new totally Tamiya compatible Battle System is coming from Impact by 01 February 09. Pretty much identical to the Tamiya system, but less expensive. It's in final pre-production mode now, molds being tweaked as we speak. Electronics are finished, tested, and approved by selected customers in the Orient. It works in any environment, and works extremely well. And for you experienced tankers out there, you better rethink your "out of range" specs, even in direct strong sun light.