I have 60k might. Is it good be part of 250k guild ppl or be a part of 60k might ppl?
Might doesn't matter so much as the strength of your heroes.
Being a part of a larger guild will pit you against stronger opponents. If you are active, and capable, most guilds won't mind lower might players.
That being said though, the difference between 60k and 250k is extremely large. Most 250k minimum guilds won't take you, simply because the amount of Guild War points you generate is directly related to your might.
However, your might may not be a problem for a 100k minimum guild.
That said though, if your teams aren't really that strong, you are best to join a guild around your might level.