The kStats Reloaded plugin hasn't been updated in the past 7 years, and offers few ways to exclude visits. It will consequently count a lot of bots, crawlers, and search engines.
WP Statistics is updated a lot more often, but since it relies on data included in the plugin itself, you can expect some bots to be included in the stats. You can find out more in the plugin's FAQ (see I'm using another statistics plugin/service and get different numbers for them, why?). It may also count your own visits.
Jetpack Stats, on the other hand, will exclude visits from logged in users by default. It also relies on the WordPress.com cloud to filter and exclude bots and other crawlers, and all calculatations happen on our servers so it won't affect your site's performance.