There are several things that may help you decide.
1) Area of coverage
The highest cost of aerial imagery is putting the planes in the air. The highest cost of satellite imagery is the desired resolution. Aerial imagery and satellite imagery are not equivalent products, so it is hard to compare the costs directly.
You can compare indirectly, by determining a per mile cost for the desired resolution. Currently, the finest resolution on commercial satellite imagery is 2.4m for CIR and 0.6 for Panchromatic. Aerial imagery can be as fine a resolution as 2 inches. A general rule: if you need a large area, the cost of satellite imagery is higher (as your coverage area increases) at a fine resolution compared to that same product in an aerial solution. If the area you need is small, you may find that the costs are the same for aerial as satellite (but you may be able to get a finer resolution with aerial).
2) Spatial resolution needed
Commercial satellite imagery is available to about 2.4 m for CIR and 0.6 for Panchromatic. Aerial imagery tends to be available in much finer spatial resolution.
3) Time of acquisition
The timing of aerial imagery acquisition is variable, whereas satellite image acquisition is on a set schedule and is more frequently acquired (although clouds can be an issue). In some situations, the time of acquisition and/or the turnaround (from acquisition to a product you can use) may be critical. If this is the case, an aerial contractor may be able to attempt capture imagery at a very specific time and day, whereas satellite imagery is generally less flexible because the orbit of the satellite is fixed. A satellite may not visit the same area more than four times a month or may not have a cloud-free capture available. When ordering satellite imagery, you usually have to be flexible on the window of time you expect to get an image from. If cloud cover is common in your area, you may not be able to consider a satellite imagery solution.
4) Revisit needs
If you have an area that needs to be monitored consistently, you may want to consider a satellite image since imagery can be acquired for the same path over and over. With aerial imagery, you will need to repeatedly contract and plan for planes to fly the same area, which can be costly.
5) Some imagery applications require spectral information?the bands of data that make up the image (e.g., blue, red, green, near infrared). Multispectral data options exist for both aerial and satellite imagery, although the resolution (number, wavelength, and width of the bands) varies considerably from instrument to instrument. With a few exceptions, hyperspectral data and LIDAR instruments are available only on aerial platforms.
6) Ease of acquisition
Aerial imagery takes more planning and processing on both your side and a contractor's side. Satellite imagery usually can be ordered through a simple process for the same area over and over again.
7) Ease of use
This depends on your application. Imagery that comes fully processed is easy to use for most visual applications. Unprocessed data from any source requires technical expertise and specialized software. Image rectification and accuracy should be considered with both products. Each require some tweaking and knowledge about image rectification and accuracy measurements.
