<prompt> Human: I have switched to a new job. My old 401k was with Merrill Lynch, and my new jobs 401k is with Fidelity. Although Im trying to learn, Im still not very knowledgeable about investing. Is there any reason why one wouldnt want to move everything from the old Merrill Lynch 401k into the new Fidelity one?  <response>: The only reasons I can think of would be your old one having better fund selection or lower fees or both, though some places wont let you keep them in there for an extended period if you no longer work for the company they were managing it for. If the funds and fees are similar itll be better to move them over since theyll be easier to manage and keep track of.Your other option would be to open a Traditional IRA and move the funds from the old place to that, since the IRA would be your personal account and it wouldnt be tied to your employer and you can roll any future 401k funds to that IRA every time you leave a job so you dont lose track of them. The other advantage is IRA accounts generally have morebetter fund options than the 401k plans so you could potentially get a much higher return than with your 401k accounts. 