I would say it depends on your current skill level and I disagree with the above....(Sorry) 2NL is easier to beat that 5NL in terms of BB (or Big Bet = 2 x bb) per 100 hands. It is quite easy to show a profit of 15-30BB per 100 hands at these stakes over a 10000 hand sample (Baring in mind that a return of roughly 5-8BB per 100 hands at 100NL would be considered crushing that level).
Starting Stack Reached.jpg
As you can see from the graph above over just shy of 4000 hands a good profit can be won at these games (I admit I was about $7 above EV here). 4000 hands, while it appears a lot, is manageable when playing 4 zoom tables at a time in one session.
Obviously a BB at 2NL however is much smaller than at 5 or 10NL so yes bankroll increase is smaller, but as a return on an investment much bigger and a much softer game. I would recomend TAG at first, however LAG will certainly pay more at 2/5 and 10NL, although this is dependant on skill level so is something you should be aiming for.
You want to be progressing as fast as possible however as remaining at 2 or 5NL for too long will reinforce some bad habits that will cost you dearly as your progress in stakes. Strict bankroll management, level shots and hand history review will aid in preventing this and moving up at a comfortable rate both in terms of BR and Skill.
Where it has been stated about value betting more (and much thinner than I would at higher stakes) and bluffing
much less this is correct. I often see people over correct for this however and play far to passive... there are still good spots for bluffing at these stakes, especially when you have stats/notes on your opponent.