Regarding "best" ... depends on how one enjoys the game.
Ok I am going to take a shot at this from a noobie point of view. I am still calling myself a noob since I have yet to play a proper game even after getting all the starters up to 8th, or even finished painting a complete unit. But when I do play games these days its very casually, meaning I don't get caught up in debating rules. Worse case scenario roll a dice for it and move on. So I am looking at this from the point of view where I am sitting and looking at a collection from various eras, and which set do I want to spend the most time on.
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I love the 4th ed starter, with additional models from the time period including those to play the Battle for Maughtrond Pass scenario (which is important as I typically dont know where to start with new armies) and I love those models. The starter has everything I need to play for awhile since it comes with army lists, and I really don't have to touch an army book. That scores huge points in my book. While I rejected the color and cartoonish look of the period at the time, I love it today. I have enough models to make 1000+ point armies for the High Elves, Goblins, and Empire armies.
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I really like the 5th ed starter. While I always thought Bretonnians vs Lizardmen was a ridiculous combination, it wasn't until I got the box set with some additional models like the Slaan Priest did my mind change. One of the rulebooks includes an example 1000 point army list for both armies using additional models so that is what I set out to build and I was shocked that not only did I like the old Bretonnians (which I didn't previously), I fell in love with the Lizardmen.
Since this starter did not come with any army lists like 4th did, I did get the Army Books of the day for both, and really found them interesting. But I don't have any desire to get anymore. And since the game appears to be close to 4th (in some cases using the same army book), I just figured I could use what I have for 4th if I wanted to mix things up since the models from that era share the same aesthetics.
* I am REALLY impressed with 6th ed starter but mainly the rulebook. I really like the models for the starter armies and I expanded on them by being inspired by what was released in their army battalion sets at the time. The great cannon, the chariot, the arrer boyz, everything has been really run to assemble. I love how expansive the rulebook is with different ways to play as well. The example army lists are a joke, and given that the set came with no other information on its armies or any others, this does get a ding, but since Ravening Hordes was released in addition to it, it might be the best one-two punch I have see in games. For a long time Ravening Hordes was my go to list to determine what I wanted to collect for a number of armies (I went on to buy models to field about 1000 point armies for every army in that book). I did buy the army books for Empire and Orcs to enjoy more of the armies but they really aren't needed. None of the army books are, and that's a big big plus for me.
* I really like the 7th starter as it comes closer to what I hope to see in a starter. 7th includes not only 2 fun looking, more rounded armies than previous editions, but also includes some terrain which I always, always appreciate. I will ding any starter set that doesn't come with some terrain pieces. It also appears that the model count was geared more for 6th edition than 7th, since units had to be 5 wide to get the rank bonus, and they included 8 miners and 12 warriors but stacked them in 4s in the pictures. I assume there was a disconnect between the set designers and the game designers. But over all the models are really nice, have lots of character, especially the Night Goblins. The whole set does look fun to get into.
After a rulebook like 6th, 7th just isn't as fun. Yes, there are other was to play the game, they published Warband rules and so forth, but I am only judging all this based on how much you can get out of the starters. No Ravening Hordes was released for this edition, so if you wanted to get into an army, or several, you had to get the books. I did buy the Dwarf and Orc army books and expanded on the starter armies, but thats really it.
* While the 8th set comes with the nicest models released in a WFB starter, its also the worst starter for me. I was stunned to find that no army list was provided in the set, just some directions on using the unit values in the appendix to work out a battle, which I just thought was the absolute dumbest thing I had ever seen a gaming company do. It was like they just didn't care. How much work would it have been to just include 2 sheets of army lists for just what comes in the box? Apparently they came around to realizing how dumb they are because they eventually released them online.
From that though, its easy to see in the rules that larger units are going to be needed for some armies, which I don't want to do. I filled out the starter armies with some additional units, but since they did not release an 8th ed army book for the Skaven, I decided to get the 7th book for High Elves. It just didn't feel right referring to different editions for the same game. I imagine an 8th ed Skaven army book would have looked gorgeous too, since the High Elf one does.
So 8th really has some nice things going for it, but some really dumb issues kills any desire to do more with it. There is no wonder this is the last version of WFB before they had to flush it all down and come up with Sigmar. This is my least favorite edition even though I love the models.
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So it should be obvious here that I like starters that give you more than just the rules and some models, but some terrain and army lists, even if those army lists are incomplete. Just give me a working taste of what else is out there. The 40k 3rd book does a good job at that. I still think that is the best 40k rulebook ever released because it has everything I need in it to play games with a number of different armies. They basically put a 'ravening hordes' in the rulebook. Those days at GW are prob long behind us, but its also why I have lost interest in keeping up with the game.
