Entrepreneur-turned-VC-turned-entrepreneur-turned-VC-again Max Niederhofer is leaving prolific investment firm Accel Partners after only a year on the job, joining another European VC as a full partner instead.

Niederhofer has resigned from his position as Vice President in Accel Partners’ London office and will be joining Sunstone Capital as a partner in its Copenhagen, Denmark office.

This will allow him to actually make his own investments in European startups, something he wasn’t actually able to do in his former VP position at Accel.

At the end of last year, Accel also lost Adam Valkin, who decided to relocate to the United States to join VC firm General Catalyst Partners as a general partner in its Boston office.

Accel has since closed a $475 million fund focused on Europe and Israel.

As for Niederhofer, he will focus on early-stage technology investments and support existing companies in Sunstone Capital’s portfolio.

The German became a professional investor in 2007 after dabbling in entrepreneurial activities. He was a principal at Atlas Venture, where he worked with companies such as DailyMotion, Seatwave and Moo, and made personal investments in startups like Last.fm (sold to CBS), OneFineStay and Skimlinks.

Between leaving Atlas and joining Accel, Niederhofer also started and sold a data marketing company called Qwerly to Fliptop.

Niederhofer comments on the switch thusly:

“I am thrilled to be joining a partnership that allows me to be an investor as well as an entrepreneur. At Sunstone, we are building Europe’s premier, early-stage, West Coast-style venture capital firm.

We want to be faster, more accessible and better to deal with than anyone else in the market.”

Sunstone’s portfolio includes companies such as Amen, Gidsy, Issuu, Layar, Paymill and Prezi. Another portfolio startup, Podio, was sold to Citrix Systems for approx. $53 million last year.

Niederhofer tells me he thought about setting up his own fund, and even talked to a few limited partners about the possibility, but ultimately decided that the fund would have to be too big for a brand new firm to make a difference in the current market.

“There’s tons of angel money in Europe, but not enough Series A capital that gets invested into promising startups,” Niederhofer says. “That means the market opportunity is in Series A, but it also means you need to raise between $75 million and $120 million to compete.”

Sunstone was founded in 2007 and currently manages around more than $900 million in committed capital across seven funds, the latest of which was raised in December 2011 totalling $110 million in fresh cash.

Niederhofer says Sunstone’s model, where everyone is an equal partner, was the model he would have chosen if he started his own VC fund, and this alignment pushed him to make the switch to the Danish VC firm.

It’s really Accel’s loss: Niederhofer was recently named “Best Startup Advisor/Mentor 2012” at The Europas awards ceremony in Berlin.