In plain words
But the yogin who strives earnestly, purified of faults and perfected through many births, then reaches the supreme goal.
Word for word
But the yogin striving with effort, cleansed of sin, perfected through many births, then goes to the highest goal.
The commentators
Bhagavadgītābhāṣyam
कुतश्च योगित्वं श्रेयः इति —
प्रयत्नात् यतमानः, अधिकं यतमान इत्यर्थः । तत्र योगी विद्वान् संशुद्धकिल्बिषः विशुद्धकिल्बिषः संशुद्धपापः अनेकजन्मसंसिद्धः अनेकेषु जन्मसु किञ्चित्किञ्चित् संस्कारजातम् उपचित्य तेन उपचितेन अनेकजन्मकृतेन संसिद्धः अनेकजन्मसंसिद्धः ततः लब्धसम्यग्दर्शनः सन् याति परां प्रकृष्टां गतिम् ॥ ४५ ॥
In plain words
And on what ground is being a yogin the better thing? — that is the question raised.
‘By effort’ means striving further still, making a greater effort—that's what it means. Then the yogī, the knower, whose sins have been thoroughly washed clean, perfected across many lifetimes—having gathered, birth after birth, a little at a time, this accumulated store of impressions, built up and perfected over many births—having finally attained right vision, goes to the supreme, the most excellent destination.
Close to the Sanskrit
And from what [ground] is the state of being a yogin better? — thus [the question].
‘By effort’—i.e. striving further, striving—that is the meaning. Then the yogī, the knower, whose sins are thoroughly cleansed—i.e. purified of sin, whose sin is cleansed—perfected over many births—i.e. having accumulated, in many births, little by little, the accumulated mass of impressions—by that, accumulated, made over many births, perfected—‘perfected over many births’—then, having attained right vision, being so, goes to the supreme, i.e. excellent, destination.