illustration (attribution, if any possible, is at the end of the article)
Naïve Mahāyānists delude themselves easily into judging Mahāyāna 'higher' than Hīnayāna, based on the supposed selfishness of those seeking arahantship.
First, this is a misunderstanding of the attainment of arahantship. An arhat has fully dropped the attachment to the conventional notion of 'self', so selfishness is basically rooted out.
Second, even according to Mahāyāna (e.g. the Lotus sūtra), an arhat will have a pause (possibly barely a single moment of consciousness) then respond appropriately to what (s)he sees (without ignorance, lust or aversion) i.e. will engage with the bodhisattva path.
So there's really no basis at all on such a naïve projection of selfishness on arhats, this is merely a self-serving ignorance of what Mahāyāna sūtras actually state.
Of course, Theravāda is not even Hīnayāna, so the debate is irrelevant anyway. The one "early school" that is still well and kicking today is not a substantialist school!
After getting rid of the most naïve projection, some Mahāyānists might pretend that "at least Mahāyāna clarified this point." The superiority of Mahāyāna would then supposedly be in relation to the ordinary people on the Path… in relation to those without major attainments yet, but nonetheless showing early more "skill in means" than Hīnayānists.
To pretend that a buddhist path ever advocated a "temporarily selfish" path is delusional, it's only a self-serving assessment by Mahāyānists wanting to be superior one way or another, wanting to "be right."
Unlike the pre-buddhist punna- based morality (doing good, with the idea that one will receive good as a consequence) which is not completely free from self-interest and self-motivation, the kusala- based morality (wholesomeness, appropriateness) introduced by the Buddha is Nibbāna- oriented and thus leads to the decomposition of the self-notion!
A sutta in the Pāḷi Canon solely and clearly states that the concern for, and care of, others starts prior to arahantship:
Monks, these four types of individuals are to be found existing in the world. Which four? The one who practices neither for his/her own benefit nor for that of others. The one who practices for the benefit of others but not for his/her own. The one who practices for his/her own benefit but not for that of others. The one who practices for his/her own benefit and for that of others.
Just as a firebrand from a funeral pyre — burning at both ends, covered with excrement in the middle — is used as fuel neither in a village nor in the wilderness: I tell you that this is a simile for the individual who practices neither for his/her own benefit nor for that of others.
The individual who practices for the benefit of others but not for his/her own is the higher & more refined of these two.
The individual who practices for his/her own benefit but not for that of others is the highest & most refined of these three.
The individual who practices for his/her own benefit and for that of others is, of these four, the foremost, the chief, the most outstanding, the highest, & supreme.
Just as from a cow comes milk; from milk, curds; from curds, butter; from butter, ghee; from ghee, the skimmings of ghee; and of these, the skimmings of ghee are reckoned the foremost — in the same way, of these four, the individual who practices for his/her own benefit and for that of others is the foremost, the chief, the most outstanding, the highest, & supreme.
These are the four types of individuals to be found existing in the world.
— Chavalata Sutta (AN 4.95)
We can spend our time arguing why a path is superior to the other, or we can spend it figuring out what brings us closer!
Criticising others is not the Path, is not "right speech". This works both ways, of course… Any idea that the teachings found in Theravāda could not possibly be expressed in a different way, that only Theravāda is legitimate and cannot be improved upon (regardless of conditions and circumstances of the audience), is as delusional as the naïve attacks sometimes presented as 'Mahāyāna'. Only a very naïve Theravādin would reject a priori any elaboration and adaptation, notably when Theravāda itself is highly influenced by thinkers other than the Buddha, be it in relation to the Abhidhamma (canonical and post-canonical) or in relation to later texts such as the Visuddhimagga.
What brings us closer? Not an opinion of superiority.
photo from tnp.org/the-center-at-dolma-ling