Most of the APRS I know of on 70cm is backbone links between nodes...
Can you tell me where in the country you have seen APRS "nodes" linked together on 70cm?
The fixed infrastructure in APRS consists of digipeaters and I-gates. In my experience, the term "node" is not typically used with regard to APRS. Digipeaters are "store and forward" repeaters that re-transmit the APRS data that they receive. Both receive and transmit are typically on 144.390 MHz (in the U.S.). I-gates just receive on 144.390 MHz and then inject the APRS data they receive into the APRS-IS database. Reverse I-gates gate some APRS data, typically just APRS messages for local users, from the APRS-IS database to the local APRS frequency, again, 144.390 MHz.
Since APRS is a real-time information system, there's not much need for "node" linking. The position reports, objects, or weather data that I might be transmitting is useful to APRS stations in my local area, but not all that useful to stations outside my area. And, as long as there's an I-gate in my area, the information I'm transmitting is available on the Internet.
Perhaps you are thinking of packet radio, of which APRS is a subset, where switched nodes gate traffic from the local packet frequency to a backbone frequency.
To the OP, if you want to take advantage of the local APRS infrastructure, i.e. digipeaters and I-gates, you will want to use the frequency that is being used in your area. For most of the U.S., that's 144.390 MHz. In some special circumstances, for example, a search and rescue event where the users are fairly localized and you don't need to use the existing digipeaters, using another frequency is an advantage because you can pick a frequency that's less congested than 144.390 MHz.
