The purpose of surface treatment is to protect the outer copper layer PCB and improve corrosion resistance.
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In general, HASL has poor pitch devices that lead to the opportunities of obtaining opens and shorts (bridging). Also, compared to other surface treatments, such treatment is often unsuitable for the use of assembling. Due to the above reasons, if you have a higher level requirement for surface treatments, we suggest not to choose HASL.
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In the past, we have seen many solder balls created within the BGA areas of HASL boards during the post-production processes for assembling. Considering your production costs match with no inquiry of BGA designs, we suggest you use HASL. However, for inquiry of BGA designs, it is recommended to proceed with immersion gold surface treatment.
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For COB Bonding production, it is recommended to use immersion gold for the high level requirement of surface treatments.
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If your PCB already applied with partial gold plating, it is not recommended to proceed with OSP surface treatment for the reason that a deposition of gold on copper may occur, resulting a poor surface finish.