difference in S3400 and D3400

[Lee Carter 150]

Used the XS site and put in my vehicles info(01 Burb).  It suggested a S3400 underhood and a D3400 aux.  I have seen vids showing the D's swelling up due to heat in the engine bay.  Yet still I see many still putting the D3400 under the hood without issue.  But I digress- the point of my question is that I plan to run both batteries under the hood.  should I use 2 S series?

 

[Lee Carter 150]

nevermind- reading is your friend- looked right over the pinned thread.  Feel free to delete this thread.