The 18" MPR is still the best entry-tier AR you can buy. The one thing that stands out with the 18" beyond pretty much all other entry ARs is the full-length gas. Even if you can match the furniture (which is better on the MPR than on this), even if you get a full-length rail (which you get on the 18" MPR and not this one), even if you get a better barrel (and the heavier-profile MPR barrel is superior for everyday use than a pencil profile), the full-length gas system matters.

The reason full-length gas matters is that what wears out first on your AR, the thing that kills your rifle fastest, is gas port erosion. The little hole drilled in the barrel wears away, widening the gas port and making the entire recoil system change for the worse. It's why many entry-level ARs will significantly degrade or even fail around 3000 rounds; the cheap gas system and mid-length gas profile add up to a lot of barrel wear. Longer gas systems give the expanding gas more room to fill; simple Boyle's law shows that more volume (aka more barrel length) reduces the pressure of the gas. This in turn generates less heat at the gas port, and less wear.

tl;dr - do some research and you'll find most everyone agrees you should get the longest possible gas system for your barrel. Almost all entry-tier ARs have mid-length gas. The 18" MPR has full-length.