d2? d2 Quadra? What is the difference

I do video and music recording and editing on a high end Mac.

• The d2 is almost $100 less for a 4TB than the d2 Quadra
• I'm looking at an additional drive to use as redundancy.
• What is the difference? They're both 7,200 rpm

I'm on my second d2 Quadra

• the first one ran 24/7 for almost 10 years and travelled around the world with me packed in my stored luggage.
• When it failed it owed me nothing. All data was recovered by my local computer guy.

Thanx for any info from anyone

Cheers

xoxo 🙂