As the name suggests crank/mid drive kits are fitted to bottom bracket area instead of front or back of the bike. They provide very high levels of assistance. Being fitted to crank they make the bike more stable compared to front or rear wheel kits. Greater stability makes sense for a heaver e type bike, easier to manoeuvre in tricky and tight areas.
On tests rides some people assume these mid drive kits feel less powered, but actually you are pedalling exactly where assistance is given so the feel is smoother you don’t get the kick associated from rear wheel drive or the jerky pull from front wheel drive electric bike kits. Mid drive kits are more sensitive to how you ride and provide power exactly where and when you need it.