Literally 妥協する is to compromise, where two parties have something in conflict. The conflict is substantial, there must be real negotiations generally. すり合わせる is more to adjust, where it has do with things being different.
As nouns, 妥協 is more about the fact of settling on something lesser. すり合わせ is more the negotiation itself.
So sometimes, the result of すり合わせ may be called 妥協, but generally 妥協 sounds more like one party (or both) really abandoning a part of its requirements while すり合わせ can be a simple adjustment.
For example, 予定をすり合わせる means to adjust each other's schedule. In most cases, I suppose people can do this without too much sacrificing. Note 予定をすり合わせる can be used also when there are no plans yet. In this case there is absolutely no sacrifice.
On the other hand, 予定を妥協する does not generally sound very natural. But if it is about a negotiation of purchase of some goods at enterprise level, 入荷予定を妥協する can sound natural, meaning (e.g.) the receiver accepts the goods being delivered later than expected.