Now granted since you don't have an address listed, I don't know whether you have access to the AMT kit or not. If you are in the USA, you should still be able to get them (the standard Round 2 reissue is discontinued, but the Tholian Web boxing is currently available and it has a little better decal sheet). If you are in Europe, the Revell kit is going to be what is available (some distributors still have the AMT kits there, but the prices are disgusting).
I would say for ease of build and a decent size, the 18" AMT Enterprise is probably the best option. It is big, its problems are well understood and reasonably easy to overcome and there is PLENTY of aftermarket for it.
I shot a video that details some of the issues I've encountered with the kit and how easy they can be to correct:
18" Starship Enterprise Building tips and techniques - YouTube
If lighting is what you want to do, the Revell kit while not being AS accurate is the easiest of the currently available Enterprise kits to light since it has the clear window inserts. Its scale is also close enough to that of the AMT kit that some of the resin parts designed to fit the AMT 18" kit should fit the Revell one.
Here is my video review of the Revell kit (a long video, but I try to cover all the bases)
Revell Star Trek 1/600 USS Enterprise In Box Review - YouTube
The Polar Lights 1/1000 kit is the most accurate, but it is small, meaning it isn't as easy to light. Still, it is possible to light if you put the time in to do it. But for a first time lighting project, bigger is better.
Others have mentioned the 22" long TOS Enterprise cutaway that AMT/Ertl did in the 1990s. They are out there, but they can be tough to locate sometimes. I would say it is a good model, but it has some weird issues related to the cutaway parts, so you would probably need to get some resin bits to correct some of those issues. Personally, for the work needed, I would probably recommend going with something more readily available at this time. But it is admittedly more accurate than the 18" and the Revell kit (1/1000 is still more accurate than the cutaway though).
Indeed as others have mentioned, we should be seeing the Polar Lights Round 2 1/350 TOS E hopefully by the end of the year (they are close to the test shot stage right now). All indications are it will be the most accurate TOS E of the lot in injection molded plastic and big enough to handle most lighting projects. But we don't know exactly when it will come out. So the wait could be six months, or it could be closer to 12 months. So if your plan is to do the ultimate TOS E, it might be best to get something more readily available right now to practice on (be it paint technique and/or lighting) then splurge on that one later.
As for long box versus small box E, yes technically the old Long Box AMT Enterprise is more accurate, but the small box kits build easier. And technically they didn't use the long box kit with the clear domes. The Constellation had no domes (since the engines were totally trashed) and even if it did, in 1966-67, they only have the first production version with the white domes (the orange domes in that kit weren't available until the third season and I don't believe they used an AMT kit in season 3 at all). The AMT kit versions were used for a very long shot in "The Trouble with Tribbles" and of course for the Constellation in "The Doomsday Machine". The Constellation footage was reused for the trashed Excalibur in "The Ultimate Computer".
Still, the older kits are perfect if you want to do one of these (crooked pylons and all):