Which monitor of the three is better?

A lot of people dislike 27" with only 1920x1080 resolution since you tend to see the pixel spacing. They then move the monitor further back so those gaps resolve but then you might as well get a 23" or 24" for cheaper.

IPS vs TN:
More specifically, RESPONSE TIME is a factor for moving video. Lower response (2ms or less) is more ideal for gaming however the non-IPS screens tend to have worse VIEWING ANGLES so the color goes off a bit towards the edges.

So pros and cons.

My recommendation would be something like this:
http/pcpartpicker.com/part/asus-monitor-vs238hp

for more money there's this:
http/pcpartpicker.com/part/asus-monitor-vg248qe

*If you want IPS then get a 5ms panel, no higher:
http/pcpartpicker.com/part/asus-monitor-vs239hp

Monitors. In order of PRICE (USD):

*I don't have time to do extensive research, but there are slight differences such as:
a) WARRANTY
b) Inputs (HDMI, DVI, VGA, DP)
c) Speakers
d) Audio output (for headphones or desktop speakers)
e) Height adjust; 90deg tilt for vertical viewing?
f) manufacture quality: light bleed, failure rates, dead pixels
g) IPS, TN etc (main panel type pros and cons)
h) refresh rate (60hz up to 144Hz)

CONTRAST RATIO for monitors doesn't really factor in anymore. The Dynamic number is meaningless to anyone buying, and the TRUE Contrast Ratios for desktop monitors all appear to be 1000:1. It's the TCR that indicates how "black" a monitor can really get. Just FYI as it won't factor in but it has to do with the light always leaking through the panel so you never truly get complete black.

The BENQ you linked originally has higher than 1000:1 TCR (claims 3000:1 but it's really lower in tests however that's nice). The drawback on this is some light uniformity issues but it's a REAL PAIN reading reviews as sometimes the issues are hyped up a bit. Unless you see it yourself it's hard to say.

So the BENQ actually sits BETWEEN a good IPS and TN in some respects.

1) $380: http/pcpartpicker.com/part/aoc-monitor-q2963pm
*Atypical 21:9 ratio (2560x1080) but some people like it. I'm not sold myself, though in the future slightly curved ones might be ideal like the new expensive LG model.
- IPS 5ms
- 29" 2560x1080 (screen SIZE closer to 27" at 1920x1080 but haven't calculated)

Similar one with only one reviewer ($350 similar specs): http/pcpartpicker.com/part/lg-monitor-29um65p

2) $270: http/pcpartpicker.com/part/asus-monitor-mx279h
- IPS 5ms
- 27", 1920x1080

3) $240: http/pcpartpicker.com/part/asus-monitor-ve278q
- TN 2ms
- 27", 1920x1080

4) $180: http/pcpartpicker.com/part/aoc-monitor-e2752vh
- TN panel
- 27", 1920x1080

Similar non-IPS:
http/pcpartpicker.com/part/asus-monitor-vs278qp


SUMMARY:
I can't pick one for you, but I advise you to decide on the main PRO and CON between IPS and TN. If you prefer less image blur then perhaps get the last monitor for $180 USD.

If you prefer IPS then the second one I linked (Asus MX279H) looks fairly nice. Again, go back and look at the Warranty duration and fine print. My Dell U2711 for example was expensive but had an awesome Warranty. It was three years long and when it died at two years I got a new one THE NEXT DAY with a pre-paid waybill sticker so it never cost me a cent.

Warranties do vary a lot such as how many dead pixels and how close the grouping, how shipping is calculated so go to the Asus or other website to find that info. Does it offer a reasonable extended Warranty? (FYI, some in-store warranties are useless as the overlap but not extend an existing manufacturer Warranty.)

If I was forced to choose from these I'd probably choose the BenQ, then Samsung and finally Asus.

All have Pros and Cons, and unfortunately I can't physically see any of them. The BenQ has deeper than normal blacks, 4ms response (lower is better) but doesn't have the overall build quality and consistency of the Samsung. It's also about $100 cheaper.

(It bothers me that the BenQ is "3000:1" as true contrast is very important. I'm bothered by why it's not done on similar monitors like the Samsung. Since it's so important it makes me wonder if doing this affects quality somewhere else. This is beyond my expertise so I just have to list all the pros and cons from reviews... )

YES. This one confirms what I thought. Good blacks, great value, but a little lacking in quality in some areas compared to the Samsung: http/www.trustedreviews.com/benq-gw2760hs-review-image-quality-and-verdict-page-2

Asus:
http/thepcenthusiast.com/asus-vx279-review-27-inch-monitor/
You can Google for more info. Sometimes Amazon has lots of customer feedback but I generally ignore AVERAGE customer scores unless you have at least 20 of them but that can be a rough guide of any issues (i.e. 2/5 reads as stay away).

*Not sure any of my other choices are any better or worse on average. Again, don't forget the Warranty and other features you may or may not want.

If you end up overwhelmed, leave it and come back the next day. If you really can't decide maybe just get the Samsung you initially linked.

(other: some monitors look better after light non-professional calibration and some look worse. I'm no good at it at least on my monitor so stick to the defaults.

*GAMING MODE if available may mean a mode in which the monitor does no video processing internally which is important to reduce lag. Additionally, I do scaling on my GPU itself (video control panel-> scale by aspect, scale on GPU) which just means I always output my native monitor resolution regardless of the game/video resolution and all scaling is done on it. This may or may not be noticeable. Probably not.

Update:
OKAY. Sorry for the LOOONG info but it was a work in progress.

*I recommend the SAMSUNG you linked first. Some links:

1) This is just to note the high average feedback score (71 people and 4.7/5 score):
http/www.bestbuy.com/site/samsung-27-led-hd-monitor-black/3924024.p?id=1219094472330&skuId=3924024

2) REVIEW: http/www.digitaltrends.com/monitor-reviews/samsung-s27d590p-review/

*None of the "cons" are dealbreakers to me. DVI isn't really needed as HDMI would be identical anyway. VESA mount is rarely used.

The lack of adjustment is an issue for sure but even if it mattered for you it's solved with a book (or better object). I'd say you could adjust your CHAIR, but ergonomically it should be adjusted to roughly achieve a 90degC leg bend.

Samsung has basically put together a very good screen in a solid, nice looking case for a reasonable price. Yes, it would be nice to have 2560x1440 but then the price for similar quality is a lot higher (my recommendations start at almost $500).