It's hard to determine which state's plan is best. The main issue is that some states offer their residents lucrative tax breaks for using the home state plan. For example, residents of Colorado can deduct 100% of the contribution amount to a 529 plan from their state income taxes. That represents an immediate return of 4.63% for the average family on all contributions.
However, some states have 529 plans with high fees and expenses than can erase any advantage a tax deduction might offer. Even more confusing, many states offer multiple plans. In Colorado, there is a “direct sold” plan offered through Vanguard which offers the company’s usual low expenses and no frills investing, and there is also an “advisor sold” plan which is sold by financial planners for families that need help in setting up and choosing their investments.
The best 529 plan research is free and offered by savingforcollege.com. They rate all the 529 plans in every state, and even offer a convenient rating system that is similar to Morningstar’s 5 Star Rating System using 5 Graduation Caps instead of stars, both to maintain the site theme, and to avoid trademark issues.
Whichever route you go, a 529 plan offers one of the better alternatives to invest for college.