The Good: The M-Series Quantum has excellent picture quality for the money, with deep black levels, accurate color and very good 4K HDR performance. Its smart system is phone-friendly, with Google Cast and Apple AirPlay control. The Bad: Less HDR punch than some competitors. Poor remote and on-screen smart TV system. Many models named M-Series Quantum won't perform as well as the one we reviewed. The Bottom Line: By bringing quantum dot color to a more affordable price point, the M-Series Quantum breaks new ground among midrange TVs. For years Samsung has been selling TVs with quantum dots -- tiny molecules that improve the color on LCD TV screens -- under its QLED brand. Now Vizio, after putting out just a single TV model with quantum dots in 2018, is going quantum with a vengeance this year. Vizio's onslaught of 2019 dots starts with the affordable M-Series Quantum, which costs hundreds less than any Samsung QLED. The M's picture is excellent, in the same league with more expensive sets like the Samsung Q7 and Sony X950G in my side-by-side comparisons. Each has its strengths and weaknesses, but in terms of pure image quality it's tough to justify spending more for one of those sets over the Vizio.But what about spending about the same on a TCL 6 series? That Roku-powered TCL is my current Editors' Choice TV, but it's more than a year old and lacks quantum dots. In my comparisons the Vizio did show superior HDR color to the TCL, but the TCL won in other areas, in particular brightness. I'd still recommend the TCL to most buyers because of its superior smart TV system, but the Vizio is still an excellent choice. As long you make sure you're getting the right model of M-Series Quantum.Some 2019 M-Series TVs are worse than othersUnlike most TV makers, Vizio often includes TVs with significant variations in the same series. Unfortunately, the differences between models in 2019 M-Series Quantum are major enough that I had to exclude the majority of 2019 TVs in the series from this review.There are two distinct sub-sets of 2019 M-Series Quantum TVs, one with a "7" in the model name (which I'll call M7s), and ones with an "8" (M8s). The M8 models cost more, have more local dimming zones and higher brightness. Otherwise the M7 and M8 have essentially the same features and specifications, including quantum dots. Here's how they break down.There are two M8 models (65 and 55-inch) and four M7 models (65-, 55-, 50- and 43-inch). I reviewed a 65-inch M8 and am confident the 55-inch size will perform in a similar way, so it's included in this review.I didn't review any of the four M7 models, however, so they are not included in this review. With significantly fewer local dimming zones and lower brightness, I don't think they'll perform as well as the M8 model I did review, so they won't get the same ratings. If I do review an M7 model I'll update this section.To make it more confusing, many retailers including Wal-Mart, Target, Sam's Club and Costco carry both M7 and M8 models (as of June 2019 Amazon and Best Buy don't sell M7s, only M8s). Currently the M8 is about $100 more than the M7. Caveat emptor.Minimalist design, sparse smartsThe cabinet of the M-Series Quantum is typically minimalist for today's TVs -- very little bezel around the screen, slightly thicker along the bottom -- but doesn't seem cheap. The corners are rounded on the top and the stand legs thin and matte black like the rest of the frame.Vizio's remote has been unchanged for years and remains one of my least favorite. Yes, it gets the job done, but compared to the simplicity of Roku and Samsung remotes, or the evolved wands of LG and Sony, it's an also-ran.The same goes for Vizio's smart TV system. The Quantum has the latest version, "Smartcast 3.0," which loads faster than before, but it's still sluggish compared to other systems, in particular Roku. With the Vizio next to a TCL 6 series Roku TV I moved through menus, launched apps and started streams from Netflix, Amazon and Hulu, and the Roku was much faster, in particular at loading its home page. Vizio has added a few apps and now allows me to rearrange apps on the bottom, but the main screen, filled with a random selection of TV shows and movies I didn't care about, is still worse than on any other current TV.App selection lags behind other smart TVs, but the major names are all there. To watch any of the hundreds of apps not part of Vizio's on-screen system, you'll use the cast function on your phone to connect to the TV. The Vizio's Chromecast built-in feature is neat for phone-centric users, but less convenient for people used to on-screen apps. The ability to use your iPhone or iPad with Apple AirPlay on Vizio TVs is coming this summer, but I didn't get to test it for this review. Vizio doesn't have any voice capability built into its remote but the TV will work with Amazon Alexa and Google Home speakers.More zones, cheaper dotsThe biggest image quality improvements over last year's M-Series are more zones of full-array local dimming (FALD) and the addition of quantum dots. FALD is my favorite addition to for LCD picture quality because it improves all-important contrast and black levels. The number of dimmable zones is an important specification because it controls how precise the dimming can be. More zones doesn't necessarily mean better picture quality, but it usually helps. Both sizes in the M8 series have an impressive 90 zones, excellent for a TV at this price level.Quantum dots, meanwhile, allow the M-Series to achieve better HDR color. The TV delivered a comparable color gamut to more-expensive QD-equipped TVs, such as Samsung's QLEDs, in my measurements.The M-Series has a 60Hz refresh rate panel -- Vizio's claim of "120Hz effective" is fake news. It lacks a setting to engage MEMC (motion estimation, motion compensation), aka the Soap Opera Effect, as found on the more expensive Vizio P- and PX-Series, as well as TCL's 6 series. All of the sizes in the M-Series use VA panels, not the IPS panels found on some sizes in previous years. Vizio supports both major types of HDR, HDR10 and Dolby Vision, in the M-Series. So does every other major TV maker except Samsung, which lacks Dolby Vision support.4 HDMI inputs (All version 2.0)1 analog composite video input1 USB portRF antenna tuner inputEthernet portOptical digital audio outputStereo analog audio outputUnlike some 2019 TV makers Vizio isn't supporting any HDMI 2.1 features like auto game mode and variable refresh rate, but most buyers won't miss them. Otherwise the selection of connections matches competitors.Picture qualityThe M-Series Quantum belted out excellent picture quality overall, largely thanks to the performance of its full-array local dimming. In dark scenes black levels were as good or better, depending on content, than the more-expensive Samsung and Sony TVs in my comparison, and about the same or slightly worse than the TCL and Vizio PQ. The other TVs got brighter in HDR than the Vizio however, although the TCL's color wasn't as good.