The most relevant page to the search term should be chosen. If the term warrants explanation, isolation and a dedicated page, then a landing page may be warranted. This would be the case in the event of a new product, new word or unique service. If it is a general term that describes the business as a whole, then a homepage may be more suitable.
It really depends, as the competitiveness of keywords varies between SEO and Bing Ads. You are free to bid on any Bing Ads term but SEO campaigns are structured around competitiveness and traffic. Any SEO keyword can be used as part of a Paid Ads campaign, but not all Paid Ads keywords can be used as part of an SEO campaign.