susana

IS good for:

1) urgency to trade is high
2) bid/ask spread is low
3) even intra-day trading voluming pattern fo the stock

VWAP good for:
1) urgeny to trade is low
2) order size is small
3) bid/ask spread is low

Brokers good for:
1) lot size is big
2) bid ask spread is large
3) market liquidity sux

so based on these I would probably go with broker.