If the room is exposed to structure, it may look nicer to run along with the tees and have pendents placed just below the tees. Aesthetics is an important factor to the architect, (if the architect is nit picky and demands you redo the layout, then that's a waste of time)
Or if there is a drop ceiling that is too close to the tees for piping below the tees to even be an option.
If there is space below the tees, and aesthetics isn't important (not exposed, storage area/ not public, etc) then usually I would go perpendicular for ease. hilti kwik hus hangers for pipes 4" or less, powers fasteners for cross mains larger than 4"
In the past I have used what we call a "Mickey Mouse" hanger.
I prefer concrete insert drilled on the vertical face of the tee. We use a beveled washer and an L-shaped angle bracket. The washer helps make the rod plumb. Just make sure you are following the concrete tee manufacturer requirements.
Is it new construction or existing? The Dewalt line is listed for cracked concrete and they bought Powers. If it's new construction the Dewalt wood knocker ll+ has a better seismic rating unless ISAT will do your seismic calcs. Snake plus, mini undercut plus
HDIP TZ looks like the best option if you are in seismic zones because it's approved by LA Dept. of Building and Safety..
We use ADHESIVE ANCHOR HIT-HY 200 SYSTEM https://www.hilti.ca/content/hilti/W1/CA/en/services/fasteners-firestop-strut/concrete-anchors/hy200-system.html
with hte all-threaded rod and the threaded side beam bracket Tolco 58
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