The long pimple rubber 388D or 388D-1

I use the 388D on 1.0mm sponge.  It's a grippy, fairly slow long pip with good control.  I like it for chopping away from the table.  It's strength is not in pure spin reversal, rather it excels in variation of spin (chop vs float).  I would recommend it, but I don't know what style you play...if you like to stay close to the table and block, check out some frictionless pips.  If you like to chop from mid to long distance, then the 388d would work quite well. 

yes it will make a significant difference.  With no sponge, the long pips effects will be increased (more spin reversal), but with sponge, the ability to create your own spin will increase.  I prefer at least a thin sponge for chopping because it gives a little dwell time which helps with control, plus it gives the ball some pace when you are far away from the table.  Some people do chop OX though...it really depends on what you want to use the lp for.