[xlr8or]

The originality vs. my way argument is very valid here. How fast do you want the car will also have an impact as ERA maintains a steady, reliable production schedule and F5 has a higher production number and can usually get a kit shipped within a few weeks.

Read the comments, don't consider any of it as gospel, read the book suggested and get what's right for you. Better to get what works for you the first time. The book may put budget at the end of the list but if you have a realistic budget its probable that there are 8 or 10 choices that will fit within it.
I think it takes most people 6 to 12 months of researching various companies to make a final decision so don't feel rushed.