First of all i tried nearly all Bots that can be found here on epvp, but for me the most stable Bot is PidgeyBot, even if the XP/H is better on other Bots, but this one never crashes and you can customize a lot, like priotize IV over CP, keep all the low pokemons like Pidgey, Weedle, Caterpie and Rattata for evolution. Use lucky eggs b4 evolution and it also supports auto egg incubators and so on.
My favourite feature is that PidgeyBot renames the Pokemons automatically and attachs the IV percentage at the end of the name, like Rattata_94. (The Bot only renames Pokemons with the IV percentage above x% you set in the settings)
PidgeyBot doesn't have a GUI, but actually I don't need a GUI anyway. Here's a screenshot of the running Bot.
