The "black frame inserted" 2nd variant is only necessary with LCD screens, they use it to mask hardware related artifacts ( panel not fast enough, draws lines upside down, whereas DLP literally spits out whole frames-by color), lot of brightness is wasted this way.
Short a: yeah, with LCD screen its like that. And plasma is similar to LCD's pattern because the hold time is short. 60hz -> 16.7ms , 120hz -> 8.3 ms. So LCD comes at ~4mS at 120hz, which is the same number as a plasma display's 4mS hold time. So in the plasma screen viewpoint , its like theres no 1. variant, but only 2nd exists.
With DLP you see with one eye all the time ( ~8mS , B,8mS ,B,8mS ....) , thats the first variant. In fact DLP is so fast, that it could do true 240hz
( ~4mS,B,4mS,B,4mS,B...) easily, it just doesnt seem necessary?? ...Maybe we'll try it with leds.
Long winded answer: in LCD 's they use something called active matrix, this sets the brightness of every pixel on the screen (it draws lines upside down). With active matrix , the pixel is held thru the entire frame time, and this is not
how CRT's , or PDP's work. ~ plus, this method of displaying constant light is actually... wrong! http://scien.stanford.edu/pages/labsite/2010/psych221/projects/2010/LievenVerslegers/LCD_Motion_Blur_Lieven_Verslegers.htm
comparison between CRT with short hold time, and LCD with active matrixhttp://www.avsforum.com/avs-vb/showthread.php?t=852878
So breaking constant light is good in one sense (reducing motion blur), but bad in another aspect, namely, since light is blocked, light is wasted. For time sequential 3d, you'd want a display where you can set the light intensity so that it entirely compensates for the glasses low light transmittance (it "peaks" with higher intensity during the open period, instead of constant but low intensity), and you wouldn't see ppl moaning about dark 3d experience on LCD's , displays like 2233rz are unbearably dark, and there isn't much comparison with DLP, apart that the "higher" resolution on the LCD won't make up for anything thats wrong, and takes its toll on GFX department.