It kind of depends on the level, book restrictions, and the type of play you want to consider.
If we are talking about level then typically psions beat out sorcerers at low-mid level and sorcerers come on top at higher levels due to flexibility and options.
Psions certainly have more low-mid level action economy manipulation with synchronicity and can essentially take more actions than a sorcerer can in a round. If most of those actions are utilized defensively in order to negate/counter the sorcerers or others actions then they cannot really do anything. As long as the psion has power points remaining they will win.
If we assume the question is whether or not a psion can beat a sorcerer at 13th level a psion is capable of doing my Mage Killer Clone clone technique which involves using temporal acceleration (augmented with power-link shards to get extra actions because I assume they are allowed; and one of the other reasons psions trump sorcerers at low levels), making a clone with fission, walking up to the enemy (with your real body), casting a wall of ectoplasm that surrounds the enemy and myself exactly 10 feet in diameter and manifesting null-psionics field. The temporal acceleration then ends and the clone can proceed to fly above the wall and pelt the enemy sorcerer with crystal shards until they are dead. Essentially the enemy sorcerer once trapped can do nothing and it is assumed they cannot make a jump check without magical assistance that would allow them to jump over a 20ft high wall. To add icing to the cake the psion can do this even flat footed because of a nifty little 3rd level power every psion should have called sense danger (Magic of Eberron).
At high level it kind of comes down to who has the first move because either the psion or the mage can lock each other down in the first round. It just depends on who gets their time-stop/temporal acceleration off first. However, I would say that since Craft Contingent Spell exists the sorcerer has a slight advantage. Both have foresight/sense danger and can act in round 0, and both have their regular contingencies, but since the sorcerer can effectively have 20 extra contingencies I would vote that in a serious fight to the death the well-prepared sorcerer would come out on top.
Not to mention access to CoP.
If we are not talking first round cheese then I would still say the sorcerer has the advantage due to invincibility combos like (shapechange - ogre mage, veil of undeath, energy immunity (acid, fire)) that the sorcerer can have up all day with rods of extend and the psion is incapable of pulling off without using experience (since metamorphosis takes exp). Of course there is the exception of a metamind/temp-reit build that is capable of doing this; but that is the only build and you sacrifice many manifester levels in order to do it.
This is all assuming you are talking about who would come out on top in a 1v1 battle which I don't think is really the subject. Otherwise you really just have to consider the fact that low-mid level the psion has more flexability, more action economy manipulation, more options with less reliance on magic items, and the ability to recharge their power points effectively giving them unlimited resources (and the ability to keep their 10/min level buffs up constantly). At high level, once the sorcerer gains access to shapechange they effectively have a whole bunch of spells and abilities for free, and near complete invincibility; so I think it has a small edge over the psion despite the fact that it is still technically a resource-based class.
