I think the popular idea that Patriots' running backs, even James White, have the ability to line up as de facto slot receivers is more than a bit overstated. White, Burkhead, and Lewis have all shown the ability to split out and beat linebackers down the field in certain offensive configurations, but these plays are more exceptions than the rule that are designed to take advantage of certain defenses.
All Patriots' backs are still beginning the vast majority of snaps in the backfield and most of the routes they run are traditional running back ones to the flats, wheels, or settling in the center as a check-down.
White probably has the best hands on the team. He's also excellent in pass pro. He plays fast, he doesn't fumble, he doesn't get hurt. He also doesn't break tackles (which is related to him not getting hurt or fumbling, since he goes down before he takes a hit). He's a great player and is capable on draw plays. He's the new Kevin Faulk.
Lewis is more of a Woodhead. Good but not great hands and both a better blocker and more powerful runner than his size would indicate. He can make people miss and punish tacklers. But he gets hurt.
The nice thing is the Patriots can afford to keep Lewis in their back pocket for later in the year. Having a healthy and fresh back who's capable of doing everything well is huge when it gets into the winter months. I wouldn't fret over his usage yet.