Question: I need an advice from someone who already faced my problem.

I have an over 10 mil. records \*.txt file to import into a new table. First, I was looking to find some "expert advices" regarding the best choice for the table Engine. 

Unfortunately I've found 50% opinions for InnoDB and 50% opinions for MyISAM. From your experience, keeping in mind the volume of information, and the fact that I will use LOAD DATA INFILE, which is the best choice for my table engine ? 
And please give me some strong arguments :) not just an advice to use one or other !

Second : After I'll decide which engine to choose, let's say MyISAM, if in the future I'll need to use the table in a transaction, I'ts a good practice to "temporary" change the engine of the table to InnoDB in order to execute the transaction, and after to come back to the first selected choice ?

Answer: 
Go SQlite, and investigate Apple's [CoreData](http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/coredata/cdprogrammingguide.html) as an option as it's backed by sqlite and a very complete package for database storage within an iOS app. 

If you want to interact with the sqlite database directly checkout [FMDB](https://github.com/ccgus/fmdb) as a good objective c abstraction layer.

A comercial option could be a package I've seen called [Locayta Search Mobile](http://www.locayta.com/iOS-search-engine/locayta-search-mobile/) - they have some good demo code
Without a doubt, use SQLite. Its performance will always beat simple JSON reading.