Two reasons to move to an IRA are:
a) A much better choice of funds. Most 401ks offer weaker funds with higher expense ratios and possibly tacked on "management fees"
b) Consolidation, to deal with fewer companies. Over your lifetime you might have 10+ employers but keep the same brokerage and/or fund company.
The better funds with lower expense ratios is the main point. My two favorite companies for retirement savings are:
Vanguard.com . The best low-expense index funds and ETFs. You can roll over directly with them if you have enough in the 401k account ($5K+? not sure). A safe, simple choice would be their "Target XXX" fund (where XXX is a year like 2050).
It's a single fund made up of their other low-expense index funds, that gives you stock and bond index funds world-wide, and that slowly shifts the balance from stocks to bonds as you get closer to retirement. This single fund gives you bits of thousands of stocks and bonds.
Schwab.com - this is a general brokerage that also offers its own index funds. If your 401k is under $5K this might be a better choice than Vanguard since I think the minimum to avoid fees is lower, and if you have a regular (non-retirement) brokerage account that helps to avoid fees too.
Edit, I disagree 100% with this:
Your Employer is PAYING someone to manage the funds for them. This is an advantage of 401k accounts over pension funds. When a company falls, they can't say "Well, we need to pay for <x> using the pension funds", because this is YOUR money. Not company money. This is one of the advantages to 401k individual investment accounts over the classic pension accounts of yesteryear.
Your employer is usually paying someone to offer second-rate funds that perform much worse than Vanguard's index funds over time. It's better than an unsafe pension fund that could be raided, but much worse than Vanguard or Schwab. If you want index funds (and you should), the 410k offers nothing of value over an IRA from Vanguard or Schwab.