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Basically power levels are a rough approximation of a units value, points are the nitty gritty.
So a squad of tactical marines has a power level of 5 (or whatever it is) and you don't have to worry about if they have a heavy bolter or a lascannon. The squad has a value for its various options.
A tactical marine squad with 10 guys is 150 pts, plus a veteran sgt. for 15 then a lascannon for 20 or a heavy bolter for 10 and on and on.
I can't imagine why anyone would want to still play with points given this set up. The points, apparently, are not even being included on the data sheets.
So many other factors go into the actually worth of a unit in a real game that small differences between a lascannon and a heavy bolter are insignificant.
Or actually are deceptive.
So a lascannon is currently worth 15 pts in a tactical squad and a heavy bolter is 5. But if you are facing off against a harlequin force probably the heavy bolter is more useful. If you are facing a Kroot force the heavy bolter is much more useful, not quite 3x as useful.
If the scenario is one where you have to get as many models across the table as possible in a short period of time, some heavier units aren't going to be worth as much as faster units, of course.
So to worry about whether this thing or that thing add 15 pts. or 5 pts. to a unit in a 2000 pt. game seems really absurd.
Even the power levels are going to be mismatched in many circumstances, although less so now that everything can hurt everything else as anyone who has ever had a dreadnought run into a squad of assault termies with lightning claws can attest.
I would imagine you will see a huge up-tick in the number of people using power level over points.
After all saying you want to play a power level 50* game at 5* points for a tactical squad with whatever they have, makes picking up an army simple and quick with math that can be done easily in your head.
*numbers totally made up by me and do not have any necessary correlation to real point values.