Buyers generally prefer an asset purchase for the tax step-up and the liability protection. Sellers often prefer a stock sale for the tax treatment. The structure is negotiated, and it affects the after-tax proceeds more than a point of multiple does.
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In an asset sale the buyer purchases the equipment, inventory, contracts, and goodwill, and leaves most historical liabilities behind. That structure can create ordinary-income recapture for the seller on depreciated equipment, which raises the tax bill relative to capital-gains treatment. In a stock sale the buyer acquires the entity with its history, which is simpler for transferring contracts, permits, and licenses but riskier for the buyer, who will want broader representations and a larger escrow. Certain assets tip the decision: an entity-held contractor license, permits that are expensive to re-issue, or customer contracts with anti-assignment clauses all favor a stock structure. This is a question for a transaction attorney and a CPA together, early, not at the letter-of-intent stage.