Im also trying to work out if we go down the AX or the Nav path.
My understanding is that AX will probably be the product that will eventually win out over the other MS flavours with a “lite” version being available down the track.
The documents I have read also seem to indicate that AX is probably the best that provides remote web access and with concepts such as virtualisation and cloud computing being touted as well as decentralisation of work forces, its something to think about.
I represent a multi country franchise system which makes remote accessability more attractive as well.
Id guess though that if you want an easier out of the box implimentation that does 90% of everything, then go NAV 
Following is a cut and paste from another site I thought was kind of useful, but might be a bit outdated…
Microsoft Business Solutions - Axapta Differences
Targeted to small to medium-sized companies with $20 - $500+ Million in revenues.
Complex Manufacturing and Distribution. Axapta is Microsoft Business Solutions’ high end system with features such as a product configurator (allows order clerks to configure a complex product with many options and features on the fly), graphical views of scheduling and Bill of Materials…
Technology. Axapta is the only Microsoft Business Solution available today that is web based. Axapta can be accessed over the internet using a browser or using the same user interface used over a local area network. Axapta uses “thin client” architecture which means that only a small amount of code is required on a workstation or remote computer. Traffic over the internet is kept to a minimum. Non web based systems require the use of products such as Citrix and Terminal Services to obtain remote access, but do this at the expense of additional complexity and expense.
International. Axapta is compliant with the legal requirements of thirty-one countries around the world.
Multilingual. You can run multiple languages, changing from one to another in real-time. Employees can work in the language of their choice and they can send documents to customers and vendors in their native languages.
Customizations. Customizations are specific not only by user, but also by location and by company. Axapta uses a versioning system for its customizations that allows you to revert back to previous versions if necessary.
Multiple Site Support. Multi-site support is ideal for companies with wide area networks that want centralized reporting and the ability to cross-reference or amalgamate information from individual offices. Customer, vendor, general ledger account numbers, and similar information can be shared or made unique depending on business needs.
Microsoft Business Solutions - Navision Differences
Targeted to small, medium-sized and some large companies with $10 - $500 Million in revenues.
Customization. Navision is known for its customization capabilities. There are many third party solutions that are available that have been written using Navision customization tools.
Rock solid performance. Customers consistently give high marks to Navision’s reliability and speed.
Dimensional reporting. By attaching dimensions to transactions, it is possible to analyze business performance across multiple dimensions.
Financial reporting. Financial reporting is based on transactions and not monthly buckets. Financial reports can easily and quickly be generated for any date range. Financial report writer also used for analysis of item ledgers – what sold, what purchased… with control over rows and columns with drilldown.
Navigation. Navision provides superior tools to easily drill down for detailed information.
Resellers. We have consistently heard positive comments on the resellers from Navision clients. Navision requires that resellers attend extensive training.
Databases. Navision was developed using the C/Side database. Navision has offered their system with Microsoft SQL Server since 1999 and today about 35% of new Navision systems are sold with the Microsoft SQL Server database. Normally we recommend industry standard technology such as Microsoft SQL Server. However, with Navision, the empirical evidence is that C/Side is fast and bullet-proof.
Granular pricing. You don’t need to purchase what you don’t use. You purchase features rather than a module that contains features that you may not use.
Supply Chain. Navision includes warehouse management, production, and returns management.
Inter-company transactions. Automatic balancing between legal entities. A PO created in 1 company creates a draft sales order in the other company ready to be approved
Microsoft Business Notification Be aware of business-critical events anywhere and prevent problems before they might occur. For example, receive notifications to tell you if there is a delay in shipping or production, or when the inventory on crucial items sinks beyond a certain level
5 pre-loaded verticals. For faster implementation for Wholesale, Furniture, Machinery, CPG (consumer packaged goods), High Tech - Should reduce implementation time significantly
Manufacturing. Includes visibility into work-in-process and support for order-by-order planning workflow (light MRP), manual planning, graphical production schedule, Gantt charts and production reporting.
Anaytics. Business Analytics with predefined or customized OLAP cubes. Pre-defined Key Performance Indicators (KPIs) for Financial Management, Supply Chain Management and Customer Relationship Management