The ArduinoUNO is a 5V device, development friendly, large, and NOT low power
The Moteino range of products are all 3.3V, development and deployment friendly, super compact including the belly mounted radio, and very low power.
Those are the fundamental differences.
So the answer about range is "it depends on a lot of factors". It has been asked a million times, but let me try to tailor it to your situation.
What gives you your range is not the Arduino/Moteino itself (not really) but the radio, the antenna and the protocol/settings used.
Anything in the 433/915/2.4ghz or above is not good at traveling up/down around hills and mountains, even with LoRa. So yes depending on your situation you might need a repeater that is in LOS (line of sight for both end node and actual gateway).
People regularly report very long ranges with Moteino and simple monopole wire antenna - even with RFM69HCW radios, so with RFM95/LoRa should give you even better results.
The use of dipoles should also help (vs just the basic monopole, especially on the receiver).
Proper use of antenna is pretty important. For monopole - keep it straight up from the GND plane of the board. For dipole it does not matter so much but if you use coax, cut it to proper length to avoid too much reflection in the coax - there are some other threads in the forum on that topic if you choose that route.