Comparing them is more difficult than you might think, as they were different documents written for different purposes. The Virginia Charters - there are actually three of them written between 1606 and 1611 - outline the rights and expectations guaranteed to and imposed upon the Virginia Company of London in its North American colonies. The charters are similar to modern constitutions insofar as they do create certain rules for how the polity ought to govern itself; the charter documents do identify some of the offices to be instituted and create certain expectations for the colonial council, but creating a form of government was the not charters' primary purpose. The charters given to the company also gave it rights to settlement and exploitation in the New World under the protection of the English crown, and this is one of the reasons why they would have been important at the time.

The Virginia Company of London was a corporation chartered by the Crown at a time when corporations were linked strongly to notions of public purpose. It had profit-seeking shareholders, but the assumption of a corporation was that it could only operate with permission from the sovereign (the Crown) and existed for for some greater public end. With this in mind, the Charters empower the company to create settlements in North America, propagate Christianity among the native population, and extract and export resources back to England. The mode of government contained therein - early Virginia was run by a colonial council with a governor at its head - was suited to this purpose. These governments were not the laws constructed for a permanent, expanding settler population. They were appropriate to what was conceived at the time to be a largely military-commercial endeavor. The same is true of the Lawes Divine, Moral and Martiall, which sought to impose military discipline on the settlement. Because corporate charters were issued by the Crown, they could be revised or revoked at the monarch's discretion. The governments created under them were neither permanent nor sovereign, and as a matter of practice, government in Virginia developed and evolved over time. The House of Burgesses, for example, was created by the Company to better govern the colony and help it meet its ends, but over time, and with relatively little micromanagement from London, the Burgesses came to behave as a sovereign parliament. Royal governors in the era after charter government would arrive in Virginia with instructions from London on what they should accomplish, but in practice they had to somehow procure the consent of the Burgesses.

The Virginia Constitution, on the other hand, was envisioned as a more permanent instrument of government, and looks much more recognizable by today's standards. Like the charters, they offer protection of the the rights of those who live in Virginia, but more explicitly and systematically. Virginia's 1776 constitution also has a more formalized separation of powers, and is organized on the lines of popular sovereignty. In a marked difference both from both modern and colonial practice, Virginia governors had few formal powers. They could not veto legislation, their powers of pardon and reprieve were very limited, and the governor could not dissolve the legislature as the British monarch could. As a republican constitution, the Virginia 1776 constitution could be amended by the people it governed.

The difference between the two is the difference between a document crafted by a monarch intended to give specific powers to a profit-seeking entity that also benefited the Crown, and an actual constitution meant to govern a republican society

Sources

You can find the Virginia Charters here.

You can find the Virginia 1776 Constitution here.

The standard history of colonial Virginia is Billings, Selby, and Tate's Colonial Virginia

There is a separate volume on the the Revolutionary period by John Selby called The Revolution in Virginia