I talked to Garmin this week.* The answer is that the 3010 and the 3210 are in fact the same unit but the preloaded charts were the only difference.* The extra cost of the preloaded raised the price up enough that sales were a little week.* So when the 4000 series came out then the 5000 the 3000's were discontinued.
My*concern was if the 3210 could accept radar and it can.* In fact it can use the new 18HD if it is connected through a GSM10 which is how Garmin connects it prepritory software.* It can also be a slave for any of the other series units such as a 6000.* It would benefit from the 6000's ability to use a NEMA2000 GPS Antenna, again by way of the GSM10.