Am familar with both. Will try to give an unbaised profile of each.
Rockhampton:
Known as "Beef Capital" of Australia.
Has CBD and major shopping centers.
Has university, state and public schools, public hospital (not sure about private hospital).
Is linked through road and rail to coal mining towns of Emerald & Blackwater.
Approx 8 hours for a one way road trip south to Brisbane from Rocky.
Is not on the coast, nearest costal towns are Bagara, Yeppoon etc.
Housing is mainly older QLD style with newer houses found in the outskirts.
Large meatworks employer closed down a few years ago, but city seems to be re-inventing it's self.
Also, Shoalwater Army training base is 50ks north of Rockhampton.
Mackay:
Known as being the "Gateway to the Whitsundays islands".
Has CBD and shopping centers.
Has university, state and private schools, private and public hospital.
Is supported by mixed business ventures eg. sugar cane and main coal port for the Bowen basin.
Is linked by rail and road to western coal towns eg. Moranbah, Nebo, Glenden.
Is on the coast with resort facilities close by.
Mackay is also a major center for the mining companies and their staff who live in Mackay and commute to the mines.
Housing is a combination of older QLD style and many new houses that have been completed or are currently being built. Generally houses in Mackay are more expensive than in Rockhampton.
By road Mackay is approx 12 hours north from Bris and 4 hours drive south from Townsville.
Okay that was my unbaised outline.
Now, my personal opinion if it counts would rate Rockhampton 7 out of 10 and Mackay 9 out of 10. Mackay is definitely in the "booming town" stage but will probably survive quite well if and when the coal mines slow down. It has many tourist attractions that would help support the local community with jobs and tourist $$$ as potential income.
Cheers,
AnneDe