The oven should not interfere with the scale’s weighing capability in any way, and is almost always a flip up design.  The oven is tipped up or raised in order to load the sample being evaluated into the center of the oven. What type of heating is used?  
By far, the most popular type of heaters is halogen lamps because they generate large amounts of radiant energy, which heats the sample quickly.  However, this type of heating, while rapid, is not uniform. It heats the exposed surfaces very rapidly and relies on the thermal conduction to heat the core of the sample.  Various heating profiles are offered in an attempt to minimize testing time.  Various automatic shutoff profiles are also a common feature.  

Where the device is being used in production control, to test product that is being mass produced, the time required per sample test is usually weighed heavily in the final decision on which unit to purchase.  Where the unit is being used in a laboratory to evaluate product characteristics test time is not nearly as important as test accuracy.   
Microwave ovens are used where more uniform heating is required and the samples being tested are compatible with microwave heating.  These ovens are larger and more expensive than their Halogen Lamp equivalents.
Ovens based upon dowel type heating rods are also offered.  These heat more slowly because of the thermal mass of the dowel rods, but provide a great deal of infra-red energy which penetrates the sample much more deeply than the radiant energy types.

In the end, the characteristics of the samples to be tested should determine the oven type.
The accuracy requirements of the analysis will determine the scale type required for the measurements.  Production control applications may require nothing more than an industrial scale (strain gauge load cell), or they may indeed require the more accurate laboratory type scale (electro-magnetic force load cell).  
Research type applications may well require the accuracy and sensitivity of an analytical balance (0.1mg sensitivity with 100gram capacity), but most frequently a laboratory balance (1.0mg sensitivity with 300grams or more capacity) will suffice.
The quality of the software is very important in making the device easy to use, and for providing direct outputs to an external computer and/or printer.

Simple in their overall concept, but very complex upon examination of their performance, these moisture analyzers require a good understanding of the characteristics of the samples to be tested in order to make a wise choice of device.