In reality, you can often make more money in a megafund PE firm, but certainly, some mid-market PE firms will pay less than investment banking. It’s also true that IB is more stable and has a clearer runway to getting promoted.
However, the key here is to emphasize what you like about private equity and why you find it intellectually stimulating. For example, you can talk about your desire to be involved with companies not just during the phase of the deal, but also helping drive and direct its growth strategy afterwards. You can also speak to your strong passion for investing and being critical and more detailed about valuation and understanding the qualitative factors, like competitors, strategic positioning, and growth markets. Finally, you can also mention the learning opportunities that would not be available in IB, such as learning how to manage and monitor the performance of senior management of a company, learning how to negotiate debt borrowing terms and contracts, and finding investment opportunities in profitable niches.