I'm not that fond of Generation 1, but I did have the 86 movie as a kid and the Ultimate Transformers guide that I'd often flip through. I am a huge fan of real-world cars, though, and I love scaled trucks and trailers that can hold said cars. I have a job coming later this month (to have some spending money) and I may get MP Convoy or Ultra Magnus. However, those are super expensive, and I'd like to test the waters with an MP car. I've been looking at Road Rage, G2 Bumblebee, and Hasbro Bluestreak, all of which are about the same price ($50-55 USD). MP Wheeljack is also a consideration, but he's close to $70.
Alternators are every good as mp's if not better if you're not going to take into account g1-accuracy, plus you could get two for the price any of those others on the list. It would however prevent you from being able to put them on trailers as they're quite a bit bigger, too big to fit on a trailer. g1-purists would probably tell you to get wheeljack, but if you're only looking at how good the car mode is as the main motivation Hasbro bluestreak is probably the best of those choices. It also probably has the smoothest transformation.
Why not go KO? Unless you're a purist who must only own the official Takara product, you can easily find knock-offs of Bluestreak, Wheeljack, Bumblebee and several others on eBay and other online site like tf-direct.com for half the price of the official product, and the quality is just as good too. You'll get a box and instructions that are almost indistinguishable, and in some cases you may get exclusive parts that they were not originally packaged with. I own 8 different KO's ranging from mini-cassettes to cars and their quality is top-notch. To get back to your question, I'd probably start with Bluestreak or Wheeljack.
I'd go for Prowl over the above but of the ones on the list Wheeljack gets my vote. If you're only collecting the Autobots and you want a Prime that matches the cars in vehicle mode scale then MPP-10 is an option. Basically an up-scaled MP-10 but he comes without the trailer and can be picked up for around half the price of MP-10. Warning - he does look a little large next to the car bots in robot mode but still. VEHICLE SCALE!
Of those my favorite is Wheeljack though its probably because it isn't a repaint like the others are.
Of those, I'd say Hasbro bluestreak. Looks awesome (I always liked him as a toy and character more than Prowl, and Smokescreen. dodges tomatoes) And hes the best priced legit MP in the US. Toys R us has him for 50.(+sales tax)
MP Smokescreen is also a good figure. KO's are pretty cheap as well, but be ready to shell out some money if you're going for the MP line. Where did you find those figures for under $60? I know MP Bluestreak is cheaper than that at TRU, but MP's sell out quick.
I'm just gonna throw this out there: G2 Sideswipe. He is definitely my favourite. The accesories all store nicely in both modes so you don't end up with alot of extra bits to lose. He actually has some expression on his face instead of the standard Masterpiece dead look. The transformation is fun and not too difficult like MP Megatron. He also comes with the sticker sheet so you can try applying those. I dunno what else to tell you, I think he's great but just about every MP is great so you really can't go wrong whatever you pick.
I'm one of the few who does prefer vehicle scale, but I don't know if MPP10 does scale with the cars..? I saw him next to MP Bumblebee and, while I know semis are quite large and Beetles are teeny, but that truck looked MASSIVE. Like, Bumblebee could DRIVE him or something. Amazon. Road Rage is $48.50ish, G2 Bumblebee is $54ish. ---- So, is Wheeljack really $20 better? I know Road Rage and Bee aren't the most bang for your buck, but is he THAT much better than Bluestreak? EDIT: for some reason I thought Wheeljack was $68 shipped from Play Asia. Turns out he's only $63. So...is he $9ish better than Bluestreak?
I'd go with Hasbro Bluestreak because you can still get him from TRU for cheap. In addition, they have a 20% off coupon for further savings. The other car bots will cost you big bucks, so you can either wait for repaints or go the KO route. Going forward, it's best that you pre-order MP's for great savings.