Answer written by real expert (not me)
The balance of military power favors Pakistan, if you look at each country’s forces in being and military readiness. The Royal Saudi Air Force, after it completes its buy of F-15 Strike Eagles and gets more Typhoons, would be a possible exception.
if Saudi-Pakistani nuclear sharing proceeds to the point where Pakistani nuclear devices remained mated to Saudi missiles (some of the Kingdom’s 538 solid-fueled, mobile CSS-5s, particularly), then It’s possible to conceive of all sorts of cases favoring either country.
While Saudi Arabia has had more money for military hardware, Pakistan arguably has a greater capacity to place nuclear weapons on targets in Saudi Arabia than vice versa, as well as greater conventional forces.
Pakistan reportedly also has or is pursuing a second-strike nuclear capacity based on naval cruise missiles which would allow them to retaliate effectively against a first nuclear strike.
Though the quality of their weapon systems may lag the Saudis’ in some respects, Pakistan has quantity going for them:
an all-volunteer army of 550,000 active troops and 500,000 reserves, opposed to the Saudi Army’s 300,000 troops, 200,000-man national guard independent of the Ministry of Defense and loyal to the monarchy and 25,000 tribal levies, so that Pakistan at full mobilization can field two soldiers for every Saudi under arms, possibly with better unity of command;
an ocean-going navy consisting of 71 warships which include submarines, helicopter carriers, destroyers, frigates, amphibious assault ships, patrol ships, mine-countermeasures, and miscellaneous vessels. manned by 36,000 active duty personnel compared to the Royal Saudi Navy’s 11 main combatant warships and fifty or so coastal patrol boats, plus assorted support and landing craft manned by 60,000, divided into Eastern and Western fleets;
The Royal Saudi Air Force is the possible exception in this picture as far as aircraft are concerned; they have 300 combat aircraft - Typhoons, Tornado IDS, F-15 Eagles and F-15E Strike Eagles. with 88 more F-15E Strike Eagles on order and an option to buy 72 more Typhoons.
The Pakistanis’ continual armed tension with India probably requires them to have a higher readiness level across the board than the Saudis maintain. Better training, proficiency, naval type mix and operational readiness probably offset Saudi advantages in military hardware.
THERE YOU GO