Both would be strong enough to be used in an above average DC neighborhood (I assume where you live in).

5/8” is typical residential use, 3/4” is more commercial. most companies won’t even tell people they have higher options when dealing with residential customers.

There is aesthetic differences with the two options, ask the vendor to show you samples, 5’x5’ ideally to see if you have preference.

We are getting quotes for 5 ft. aluminum fencing for our backyard. We have kids and dogs. One of the sales reps said he recommends the higher grade 3/4 picket for our scenario because the 5/8 can be fairly easily bent. Any opinions on this? The 3/4 is $1k more for ~225 ft. bringing the higher grade to about $10,000 vs $9,000 for 5/8. Ouch. The other two companies we got quotes from only offered 5/8 picket so I'm wondering if this is even something to worry about.