I think iAd works best when it's possible to create a fresh immersive experience. If you're only using the platform to repurpose content a user could easily find elsewhere, it may not be worth their time or yours. If the product or message supports development of content that provides value, entertainment or otherwise, for a user, the platform offers ample opportunity
AppLovin is particularly well suited for gaming campaigns where it is really hard to reach users and you need formats like the rewarded video to keep users engaged with your ad. I would not recommend it for branding campaigns as their formats are more performance-focused and the inventory is expensive so unless you are trying to reach the desired CPA, it would not be worth it to pay that much for ad placement.
AppLovin has been a great partner for us. We have used them through our DSP and gotten great results with them. Their focus is on monetizing publishers' inventory and they could put more resources into their standalone service as an SSP to make sure DSPs can consider them strategic partners for the long term.
AppLovin's support team is their weakest point. They are not very responsive and they tend to provide solutions that do not fix the problem. It seems like they will only be proactive if you are a very big client and by doing that they are preventing the rest of the client base from increasing spend on their platform and growing their accounts
In some instances, we developed an experience for AdMob simultaneously with our iAd experience, working with both teams on a daily basis. While the Google team was skilled, receptive and helpful, Apple device functionality was broader and thus allowed for a little more imagination in bringing intuitive relevance to the creative content we developed
Of all of the competitors above, AppLovin is the one that is more focused on gaming and that has a better pool of users in terms of conversion rate. While PubMatic and Magnate offer better solutions for CTV, AppLovin is better than InMobi and MoPub regarding in-app formats and inventory.