By the way, one thing I have forgotten: an instant-forward has much less latency (obviously), but it cannot retract packets that were corrupted during receiving at the ingress port - simply because the checksum can only be calculated when the whole packet is in the buffer.
So basically you choose between safety (corrupted packets do not travel as long, because they don't even reach the final station) and latency (e.g. 10 hops a 0.12ms = 1.20ms delay on 100MBit/s), and also for the cost in buffer memory.
By the way, one thing I have forgotten: an instant-forward has much less latency (obviously), but it cannot retract packets that were corrupted during receiving at the ingress port - simply because the checksum can only be calculated when the whole packet is in the buffer.
So basically you choose between safety (corrupted packets do not travel as long, because they don't even reach the final station) and latency (e.g. 10 hops a 0.12ms = 1.20ms delay on 100MBit/s), and also for the cost in buffer memory.