Here's a blog post from Oblivious Investor, a frequent poster here:http://www.obliviousinvestor.com/should ... to-an-ira/
My take on this is, about the only advantage (aside from the possibly advantage of asset protection and the possibility of early retirement) of rolling over the old 401(k) to the new 401(k) is to keep your backdoor Roth IRA eligibility.
If you're above the Roth IRA income limits, then by all means roll the old 401(k) over to the new plan if the new plan is better, if that enables you to do backdoor Roth IRA.
But if you're under the limit, then I'd transfer to an IRA unless your 401(k) doesn't allow transfers in from an IRA; double-check this with your plan, as each plan can have different rules. If one day in the future you get to Backdoor Roth IRA territory, then you can just transfer your traditional IRA into the 401(k).
True, the fund expense ratios in the new plan are only a little bit higher than what you'd pay in an IRA, but find out for sure if you're not paying additional expenses for total assets under management (AUM) for the current 401(k). I've seen plenty of posts here with people who used to feel all happy about their 0.05% ER funds until they found out they're also paying a 0.35% AUM or more on top of that. That's why I'd be cautious about rolling over money into your new 401(k) plan until you're really sure what your expenses are.