I hope the topic wasn't too confusing, let me explain. Ive noticed many receivers that I am in the market for have an identical model that is a transceiver. In some cases, the transceiver version is cheaper and easier to come by. Example, the Icom R75 and the Icom IC-718. Or the Kenwood R5000 and TS-440S. Is their an advantage over the receive only versions? My list of comparisons could go on forever!
I don't think there is a simple answer to this, and you would have to assess on a case-by-case basis. Just because they (the dedicated RX and the TRX) look similar, or even have similar performance specifications, do not make them identical. It is often less expensive to reuse parts (when possible) across multiple radios; knobs, speakers, displays, etc. And then there is the whole brand recognition thing, along with "matching" radio lines. So that radios that are designed around the same time, and by the same teams, may look very similar, even identical.
Today the R-75 is no longer made, while the IC-718 still is. So the -75 is harder to find, and if you can find it it is often more expensive. But when the -75 was in production you could find them both just as easy, and the RX was the less expensive of the two. While the cost delta at sales points was fairly small, typically $150 or less between them, the list price, from Icom, for these radios was much further apart.
As I said, just because the dedicated RX and the transceiver look nearly identical does not mean they are. I have often heard it said that the IC-718 and the R-75 are the same receivers, with a transmitter section added to the -718. But are they really? The answer is no, not the same, but they are similar.
At the most basic level the R-75 is a triple conversion receiver, and the IC-718 is a double conversion receiver. This is a rather large difference in receiver design. The R-75 has at least one filter, in its second IF, that the IC-718 simply cannot have. The two receivers do not cover the same frequency range, the R-75 goes up to 60 MHz, the IC-718 has half the coverage, stopping at 30 MHz. This is a pretty significant difference in receiver design. There is a difference in the way the band pass filters and high / low pass filters are configured, although the basic design at this point is very similar.
Looking at the schematics you can see that some circuits are common to both radios. However that is not unusual since they came out of the same engineering house. Engineers are creatures of habit, if something works and you have used it before in a specific application you will at least consider it in the next similar application.
So yes, some circuits are common, even a lot of them. But, the specific layouts, even with similar circuits, are very often different, this can often mean different performance even for the same circuit.
The physical layout of the receiver sections of both are very different. Although the physical size of the two radios are very similar there is a lot more functionality in the same enclosure on the IC-718. There are 3 circuit boards in the -718 that the -75 does not have at all and the filter unit of the -718 has both transmit and receive filters, where the -75 only has receive filters and they are all on the Main board. None of the 4 main boards of these two radios look even remotely similar between the two, although a couple of the smaller boards are similar.
The Icom IC-718 and the Icom R-75 were designed by the same company. Their receivers were designed to do the same basic tasks. They were designed fairly close to each other in time (and so in technology). They were designed with similar price points. They can't help but be pretty similar, but that does not make them identical.
And so, as I said before, you must consider each in a case-by-case basis. And that can be tough. In general if you are looking just for RX there is no advantage to getting the transceiver. But sometimes there is no disadvantage either. Taking the example of the Icom R-75 and the IC-718 specifically, I have used both side-by-side. I found the R-75 to be the better of the two. It was more selective, it was a bit quieter, and it was a bit more versatile. But unless you can set them next to each other you probably will not notice any differences. And the R-75 is not made any longer. When both were in production I would have taken the R-75 if I had no specific need / want for a transmitter. In fact, I did, twice, select the R-75 after the IC-718 was introduced.
T!