Dacca versus Murshidbad

 If you mean Murshidabad vs Dhaka during the Mughal period, the key point is that they were not rivals for the whole Mughal era. Their relative importance changed dramatically over time.

Murshidabad vs Dhaka

	Murshidabad	Dhaka (Dacca)
Mughal-era rise	Rose to prominence mainly in the early 18th century	Became important much earlier, especially under Islam Khan
Political role	Became the capital of Bengal's nawabs	Became the major Mughal provincial capital of eastern Bengal
Period of greatest importance	c. 1700–1757	Particularly 17th century
Strategic importance	Located in the western/central Bengal river system, closer to Bihar, north India and major revenue zones	Ideal base for controlling eastern Bengal, river routes and the frontier toward Assam/Arakan
Economy	Banking, revenue administration, silk, textiles and long-distance trade	Major centre of fine muslin, textiles, river commerce and shipbuilding
European connections	English, French, Dutch and other European commercial interests became increasingly important	Major European trading presence, especially around textile commerce
Architecture	More strongly associated with the Nawabi period than the high Mughal period	Strong surviving Mughal architectural legacy: Lalbagh Fort, Bara Katra, Chhota Katra etc.
Historical significance	Capital from which the semi-autonomous Nawabs of Bengal governed	The great Mughal administrative and commercial centre of eastern Bengal

The crucial historical sequence

Dhaka was the Mughal capital first. Murshidabad became the political centre later.

In 1608, Islam Khan shifted the provincial capital of Bengal to Dhaka, then known as Jahangirnagar, during the reign of Jahangir. This reflected the Mughal priority of consolidating eastern Bengal.

Dhaka subsequently became a major centre of administration, military power and commerce.

But by the beginning of the 18th century, the centre of gravity shifted westward. Murshid Quli Khan transferred the capital from Dhaka to Murshidabad around 1704. Murshidabad then became the seat of Bengal's increasingly autonomous nawabs.

Why did the shift happen?

This is the really interesting part.

Dhaka's strength was eastern Bengal.
It was superbly positioned for controlling the delta, eastern rivers and eastern frontier.

Murshidabad's strength was Bengal's enormous revenue machine.

As Mughal Bengal became increasingly wealthy, the administration became heavily focused on land revenue, banking, silk, textiles and connections with north India. Murshidabad's location was more advantageous for the new political economy.

And the man who transformed this was Murshid Quli Khan.

He was essentially the bridge between the Mughal provincial administration and the independent Nawabi state that emerged in Bengal.

A fascinating contrast

You could summarise the two cities like this:

Dhaka was the Mughal gateway to eastern Bengal; Murshidabad became the financial and political capital of Bengal.

Or, for a presentation:

Dhaka = Mughal Bengal's eastern military-commercial capital
Murshidabad = Nawabi Bengal's political-financial capital

One important nuance

Don't call Murshidabad simply a "Mughal city" in the same sense as Agra or Delhi.

Its greatest glory belongs to the transition from Mughal provincial rule to the Nawabi period, particularly under Murshid Quli Khan, Shuja-ud-Din, Sarfaraz Khan, Alivardi Khan and Siraj-ud-Daulah.

Dhaka, on the other hand, has a much stronger claim to being a 17th-century Mughal imperial city.

This makes a very good story for your heritage website:

Akbar → consolidation of Bengal → Dhaka/Jahangirnagar → Murshid Quli Khan → Murshidabad → Nawabs → Plassey.

It gives you a clean narrative of how Mughal power in Bengal evolved into the Bengal Nawabi state.