As usual, the general answer is, "it depends"
The first generation 737s (-100, -200) are the same height off the ground. The "Classics" (-300, -400,
-500) are a little higher. The "NextGen" versions
(-600, -700, -800, -900) are higher (slightly) still. Ok, that cover's the differences in height above the ground.
With respect to "tailstrikes" (what we call them in the biz), a major factor is fuselage length. Tailstrikes on the -100 and -200 have always been fairly rare. Out of the remaining versions, the ones with the longest fuselage are the -400/-800 (pretty much the same length) and the -900 (which is even longer. I know the -400 has a small tailskid/strikeplate, and I presume the -800 does and -900 will as well. The -300/-700 (also pretty much the same length) are as not long as the -400/-800/-900, and not as prone to tailstrikes as they are, although they do happen on occasion.
The main factor behind tailstrikes isn't so much fuselage height above ground but (1) amount of fuselage aft of the main gear, combined with (2) excessive rates of rotation during takeoff. Although more rare, tailstrikes can also occur upon landing.
Hope this makes sense...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.