Is there any reason to spend an extra $100 for what is essentially the same monitor?

Solution
That list is crap for the most part, don't refer to those sites.
The only panel with a real grainy issue is the S2716DG which has a slightly grainy anti glare coating which can be annoying.
Has relatively good colors for a TN though.
PG278Q was a nightmare for BLB and poor colors, S2416DG is fine, and the other rankings are inaccurate.
The XB270HU uses a near identical panel to the 271HU and PG279Q, just has a worse stand, i've used both, I know.
Viewsonic uses offfcut or B grade panels from major manufacturers that don't meet others' standards.
However, having the XB271HU, I can't even get 165Hz to run properly, stutters all the time and cuts out occasionally.
What's your planned PC budget?
G-Sync isn't that great tbh unless you're already running with a 1080, which is what I had when I made my purchase (top of the line at the time).
In this day and age the money for G-Sync can be spent to get a 1080 Ti instead generally.
https://au.pcpartpicker.com/product/c298TW/asus-monitor-mg279q
As long as it's a good 27" IPS panel its fine.
 


Do you have a source on this statement? I did some digging round elsewhere and from what i can see, the acer and viewsonic panel are nearly identicle.

I also came across this:

Best 1440p 144-165hz Nvidia G-Sync Monitors:


1.) Viewsonic XG2703-GS (30-165hz Nvidia G-Sync) AHVA
2.) Acer XB271HU (30-144hz Nvidia G-Sync) AHVA
2.) AOC AG271QG (30-165hz Nvidia G-Sync) AHVA
3.) Asus PG279Q (30-144hz Nvidia G-Sync) AHVA
4.) Acer XB270HU (30-144hz Nvidia G-Sync) AHVA
5.) Dell S2417DG (30-165hz Nvidia G-Sync) TN
6.) Dell S2716DG (30-144hz Nvidia G-Sync) TN
7.) Asus PG278Q (30-144hz Nvidia G-Sync) TN

The Viewsonic XG2703-GS uses a 27" 2560x1440 resolution 8 Bit AUO AHVA panel (M270DAN02.3), a nearly grain free matte coating, has excellent color presets, a nice dark matte black bezel which increases the perceived black depth (dark matte grey is the best), very fast pixel response times and a 165hz refresh rate. G-Sync (compatible Nvidia GPU required) works from 30-165hz/FPS, and eliminates screen tearing and lag. The Viewsonic XG2703-GS also has ULMB (back-light strobing, excellent 1080p scaling unlike the Asus PG279Q, and superior 60hz overdrive with less overshoot ghosting than the Acer XB271HU. The Viewsonic XG2703 is the best all around 27" 1440p AHVA 144-165hz monitor with Nvidia G-Sync for PC and console gaming, and watching 1080p content.

The Acer XB271HU and AG271QG tie for second place while the Asus PG279Q comes in third. They all support Nvidia G-Sync (native 144hz; can be overclocked to 165hz), have a nearly grain free matte coating, use AUO AHVA panels which offers far better colors and viewing angles than TN panels, and have an HDMI input. The Acer XB270HU comes in fourth place since it uses an AHVA panel with the same coating, but it uses a glossy black bezel which ruins the perceived black depth (Microsoft Paint Example & Monitor Example), only has one input (Displayport), and has marginally slower pixel response times than the other AHVA panels with G-Sync. Unfortunately the 27" 1440p matte AHVA panels suffer from poor quality control; back-light bleed and unique issues like yellow/brown stains in the corners are common.

The Acer XB271HU scales 1080p better than the PG279Q, but suffers from noticeable overshoot ghosting at 60hz which makes neither monitor optimal choices for both PC and console gaming. I recommend buying the XB270HU and using the money saved to buy a quality 25" 1080p IPS panel. Best Reviewed Flicker Free 24-25" 1080p IPS/PLS for PC and console gaming if the Viewsonic XG2703-GS is not available.

The Asus PG278Q comes in last place because it is very expensive, uses the grainiest matte coating used by a 1440p monitor since 2011, often comes with pathetically low average gamma (1.7 gamma average=washed out colors) and has many quality control and functionality related issues.
 
That list is crap for the most part, don't refer to those sites.
The only panel with a real grainy issue is the S2716DG which has a slightly grainy anti glare coating which can be annoying.
Has relatively good colors for a TN though.
PG278Q was a nightmare for BLB and poor colors, S2416DG is fine, and the other rankings are inaccurate.
The XB270HU uses a near identical panel to the 271HU and PG279Q, just has a worse stand, i've used both, I know.
 
Solution
In my opinion? No. I recently purchased the Viewsonic, and it's been amazing, definitely the best monitor i've ever had.

It has minor BLB, but not any worse than any other IPS panel i've ever seen. Save the $100 and put it towards the steam sale or something.