Index method for very few updates and many inserts

Question

I am using Postgresql 9.1 with *pg_trgm* extension. I need to create an index on a text-based field. I do not need full-text searches, I use ILIKE queries to make my searches.

I will use pg_trgm but do not have much experience with gin and gist indexes. I will have many INSERT statements (~15000 daily) and very few UPDATE statements (may be 1 or 2 in a week).

What will be the index update overhead for a gin index on a such table? Or is gist more suitable?