During rate cut cycles, small and mid cap stocks tend to outperform large cap stocks. This is mostly due to their higher degree of economic sensitivity just because they are smaller is size.
After a 40%~ runup in 2024, I wouldn't say midcaps are as discounted as they were during peak rate cycles, but I also wouldn't state they're overvalued either. Further rate cuts and a pickup in economic activity could see them outperform large caps, at least from a historical perspective. The issue we have now with all off these gigantic technology companies is whether or not this will ring true moving forward.
XMMO is a pretty solid fund. It's got some diversity in terms of its holdings and it is relatively low fee (0.3%) considering the factor strategy it follows (momentum).
The only thing I'd say is that momentum ETFs are likely to witness a bit more volatility than normal ETFs. However, if you're comfortable with it and you're bullish on mid caps, certainly worth a look.