Solar panels for grid-tied systems come in two main sizes, depending on the number of solar cells they are made from. 60 cell panels are about 1.6m tall and 1m wide, 72 cell panels area about 2m tall and 1m.
Larger panels are not better because they are bigger, they will generate the same energy on the same area of a roof as smaller panels. i.e. the performance of 5 X 72 cells panels will be identical to 6 X 60 cell ones with the same energy and the same roof area. The choice is about which size of panel will best fit the available roof space.