What is the benefit of synchronizing data? Improved performance in terms of its accessibility. The penalty is some wasted storage, due to increased record size (filler spaces become part of the record).
Level 01 items and pointers are aligned on 16-byte boundaries always, whether synchronization is specified or not. You are allowed to specify synchronization only for elementary items. It is not permitted for group items.
Figure 1 illustrates the concept:

Figure 1 shows that A and B are always aligned on 16 byte boundaries. Without synchronization, A2 and A3 are stored contiguously regardless of size. With synchronization, a 4 byte boundary is chosen (due to A3's type), and A3 is aligned accordingly. There is a one byte filler between A2 and A3. However, A3 should be accessed faster.