I slide.  I have to.  My ACL is still partially torn in the left knee (though stable) but one mistake planting could be the end.  Also, at age 56 I think sliding is less wear and tear on my already old joints. 

I have been working on planting instead of sliding. Planting helps me get the ball further out on the lane. I also seem to have less timing issues.

I plant. I tried sliding for so long, but it really THROWS off my timing so bad, it’s not worth the effort anymore. Much more comfortable planting.

I slide.  Always have.  That can be difficult at my home center because they don't spend a lot of time on keeping the approaches in good shape.  It seems that synthetic approaches don't give a great slide unless they are kept meticulously clean. Thus, teflon.

A fellow bowler decided to switch to a planting because he kept having trouble getting a consistant slide in our center.  I warned him that at age 65+, that probably was not the wisest decision but he continued for several months with the planting.  After that, he said his knee was hurting and decided to go back to sliding.  I passed on (again, he didn't follow through on it the first time) the information that Charlest had given me years ago - try teflon discs.  I took one of his spare soles and cut out holes in them and gave him several teflon discs (again).  This time he tried it and he is now a happy slider, no longer troubled by inconsistant approaches.  The teflon smoothes everything out.  And, by having several holes available to either use the teflon or the cut-out sole pieces, he can adjust the amount of slide for the current approach conditions.

I like a short slide.

 There's a millions heel and sole options and I typically use one heel and sole. As the one sole wears down it becomes the sole used for tackier approaches and I buy a new one to use for slicker approaches.

I use the brown number 2 sole and the cleat heel.

Plant.  Found it eliminates any concerns with tacky approaches plus allows me to utilize my legs to generate speed and power.  As an added bonus, don't need to put on a goofy slipper over my shoe when I go to the bathroom.

The biggest problem I see with the plant style is the stress it puts on the slide knee. I have two friends who plant, now in their 40s, suffering significant knee issues that have essentially ended their competitive bowling lives. 
 
We don't stay young forever....