Why the obsession about choosing x or y? China is the main trade partner of KSA and a trusted partner on numerous key military areas such as our missile program, drones, laser weapons, mineral cooperation and 10's of other areas.
US Is a trusted (for KSA), mostly, partner and ally since WW2. We have the closest military relationship with them (overall) which has given us access to state of the art US weapons (THAAD, Patriots - which have been proving their worth for 10 + years in a excellent manner - also due to the brilliance and track record of this branch of our army:
en.wikipedia.org
F-15SA (most advanced F-15 in the world - more advanced than the US version - go look it up), F-35, Abrams, new advanced US drone deals etc.
KSA is not a NATO member nor aligned (officially) with any global power. We are and should continue to take advantage of this and the fact that we have very cordial ties with the US and China (few countries can claim that), despite differences here and there (like any relationship) and do what serves KSA's interest best.
Also the results of long-term planning is often seen much later. KSA's relationship with USA is completely different than in 1991 for instance. KSA is acting from a much stronger position and now the relationship spans every field from education, AI, renewables, science (supercomputers etc.), military, economy etc.
No such thing to make it brief:
(1.2 million views).
Trump claimed 100's of times in public that KSA would never get the F-35. 8 months ago that changed with the deals signed and KSA became the first Arab and Muslim nation to get the F-35. As well as other highly advanced US military tech. As well as access to very advanced chips, semiconductors etc.
mei.edu
Simply put, KSA is too important and crucial for the US so they will go a long way to prevent KSA from pivoting completely towards China.