which method is better when dealing with cell arrays

assuming we have a cell array containing some data coming from some data files that was structured in two methods:

1st method:

cell array of two columns, first column has the data file name, second column contains in each cell another cell array that contains a table in each of its cells, as in the image below

2nd method:

cell array of number of columns equal the maximum number of columns we may have and each cells contains a table (expanding of the cells in the first method) as in the image below

now, I have the folowing doubts:

1. which method of sturcturing would be better in terms of time and effeciency having into mind that we are going to apply it to a huge number of data files (more than 10,000 files)?
2. if the structuring would not affect that much, which one would be more faster when searching through the tables and extracting them?
3. each table of these contains data that happened at a specific time, the time is one of th variables in a table and its unique for a table, given a certain interval of time, how we can extract the tables that has data accured in that interval of time? I have managed to do that for one table at a time knwoing the file name and the time but what if we want to search through this whole 'database', how can we do that?

[Stephen23]

Method 1 is better.