i notice most nema heads i see today have buldges on the side where the ballast bracket screws in...i've seen older GE,LM,and Westy Nema's and i notice some of those lack these buldges on the side,because the ballast mounts from the top of the head,where the photocell usually is,i like all nema heads,but especially like the ones with the ballast mounted to the PC end,because it gives a very clean apperance,do they still make nemas of this style?

The bulges on the side can also hold the socket mount.  My ITT LPS NEMA has a top mounted ballast with the socket mounted to a crossbar at the bottom of the housing (in those bulges).  I like that layout best 
Some models have the ballast welded to the socket bracket.

the Nema's that have the Buldges on the side are probably easier to service since the screws that hold the Ballast/Socket assembly into the head are easier to access.

some of the bulges are for the screw in reflector option....my SA-201 has top ballast mount, bottom ballast mount, 4 screw ballast mount and the reflector screw in option!

The Philips Grooved heads (not NEMAs), those grooves are where screw mounts inside are.  They are mainly for the reflector/refractor mounting screws and the grounding screw.

i've seen some of those Grooved Heads your talking about...one of the Few Examples the Word Yardblaster will be used in the Same Sentence as Quality....i notice the nema's that have the Buldges on the side of the head,also have corosponding Buldges on the Reflector.