SSIS slow performance to insert short rows
There are a lot of things that come into play in regards to the performance difference.

1) is hardware\Instance configuration (RAM, Disk IO speed, Disk Size, Block Size, SQL-server memory configurations, Other software and tasks running)

2) Business of the server, If their are concurrent operations that it your tasks is awaiting resource access to.

3) Query Optimization.  Perhaps you are doing a full table scan on the 58 bytes but the 2MB is fully contained with in an index.  also perhaps there is more repetitive data in the 2MB.  If you have built the Select Statements in T-SQL copy them into SSMS and look at the execution plans.

Perhaps there are differences between 2012 and 2014 but I haven't seen huge performance differences in moving my packages to 2014 yet.