I consult both. I find that the expert reviews generally appreciate the smaller details a bit more, and are generally more enthusiastic about the technical brilliance. For example, you'd hardly find a mention of a VGT or hydraulic lash adjusters in a typical ownership review. But then again, the expert reviews, even the long term ones, sometimes leave out stuff like service experiences. A staff from Autocar India or Overdrive mag would hardly ever have to deal with staff trying to cheat them. They receive exceptional service and are thus less reliable when it comes to such things.
Typical owners are usually more forgiving of their car's faults, (I am) because they don't want to admit that they made a less than perfect choice. On the other hand, an owner will scream bloody murder if they have to shell out cold hard cash for maintenance and repair. For example, my car has not cost me any serious money out of my pocket so far, and thus I am happy with it. But I think I'll be a lot less forgiving if I had paid more money buying it, or had to spend a lot on maintaining it. Comparisons are a lot easier if you haven't committed to anything.
But I find that most of the faults that expert reviewers harp on, like bad plastics, are things that the average owner wouldn't really care as much about. From reading an expert review, you'd be under the impression that the Volkswagens/Skodas are the only cars in India with plastics that you can actually touch without recoiling in disgust.
You'd think that no car with an engine smaller than 1.6L could be fun to drive. You'd think that the Swift and Ritz are the only cars in the 1.2L segment that aren't slow, sluggish and unrefined.
It might be a side-effect of driving for performance tests, and not really having to worry about fuel efficiency, but personally, I feel that expert reviewers forget that most owners never take their cars to the redline, or cross 90kph. Thus, for most of them it wouldn't matter that the engine is rough after 4000rpm, or that it takes its sweet time to get from 80 to 120 in 5th, as long as you don't need to change gears too often in traffic, can inch along at 40kph in 5th gear and overtake with the AC on. I'm not discounting performance altogether, oh no, I'm just saying, be realistic. Saying that a particular car is not for the enthusiast is a lot better than calling it underpowered.
If plastic quality was such a big factor in the buying decision for most Indians, the Alto would not be the biggest selling car. A typical car buyer's priorities would be fuel efficiency, reliability, comfort, low service costs, brand value and good looks. While an expert review would take these facts into account, they would not be as important to the reviewer as it would be for an owner. An actual Palio 1.6 owner would be a lot more distressed by 8kpl than a reviewer would, and would enjoy the car a lot less. Case point being Swift petrols being driven sedately in the highest gear, while Altos (sometimes) and Swift diesels tear through traffic.
Recently, there was a comparison between the Skoda Laura diesel and the Chevy Cruze in one of India's leading magazines. They rated the Laura higher on everything except maybe design, and declared it the overall winner. They rated the Laura's interiors higher, because the plastic quality was soooo good, even though the Cruze has the freshest looking interiors on any car in that segment. I've sat in both cars, and I have to say, I found the Cruze more appealing. It felt good to sit in a space-age looking cockpit, surrounded by contemporary piano-finish surfaces, blue backlit switches and so on. I admit that I haven't driven it yet, but reliable sources say that the Cruze's common rail motor is a real firecracker compared to the pump-duse motor in the Laura. Not to mention, Skoda's un-stellar reputation on service, vs Chevrolet's excellent one. Clearly, factors like a lower price, higher FE, fresher design and better service did not matter enough to said magazine's staff as much as it would to the typical owner.
A prime exception to the 'scathing reviews' rule would be the Malayalam auto mags, which are generally highly appreciative of every aspect of every vehicle they review. There is never any strong criticism, only suggestions that 'this would have been better had it been done like that'. It's almost laughable how the tone of the article changes from start to end. For example, I was reading the review of the Apache RTR160 Hyper Edge. Now, this is NOT a comprehensive makeover of the bike, and largely a sticker and paint job, with some small tweaks. The review starts out by addressing the bike by name, but by the time the reviewer begines commenting on the bikes performance and handling, he has begun to shower affection on this bike, calliing it 'him' and 'he'. It borders on the ridiculous. This is the other end of the spectrum. I strongly suspect that these mags have to beg manufacturers for a car to review.
Everything that I have posted is just my opinion, and is a product of my experience and worldview. Please don't take offense. Feel free to criticize.