Benzoyl peroxide (BPO) is the single most effective topical anti-acne ingredient. The combination of benzoyl peroxide (BPO) gel with Clindamycin is more effective and much less irritating than the different combinations you could use with Adapalene. Of your 2 products, the one with BPO will be much more effective. However, there is no logic to mix them in one application. If you'd like to use both, you can use different topical gels on alternate days.
That being said, I would caution against any long-term use of topical antibiotics for acne (including Clindamycin) as it can lead to bacterial resistance and worsening of acne overtime.