Oppo's latest R11s and R11s Plus smartphones, released more than a month ago, are the respective upgrades to the Chinese company's R11 and R11 Plus flagship duo, which have been out for only six months before this refresh.

The R11s line overhauls the R11 line's generic-looking display, turning it into a contemporary, bezel-less design, as well as adds nifty features such as face unlock and what Oppo claims is an artificial intelligence-powered selfie camera.

But everywhere else where it matters, such as the camera, processing capabilities and software, both the R11s and R11s Plus remain fundamentally the same phones as their predecessors.

The key design change is the new display, which has the 18:9 aspect ratio that is all the rage today. This aspect ratio also puts a much larger display into a smaller phone body and makes the R11s and R11s Plus the first Oppo phones to cross over into the bezel-less look.

The result is a phone that looks sleek - like a Samsung Galaxy Note8, rather than the Apple iPhone that the company is fond of cloning.

The R11s sports a 6-inch display, while the R11s Plus is significantly bigger and wider with a 6.43-inch display. The lack of a bezel means they do not look intimidatingly wide, but I did find the Plus to be pushing the limits as comfortable phone sizes go.

The phones' full HD Amoled screens are capable of good brightness and colour reproduction.

Both phones have a slim profile with pronounced curved edges. The design is fine on the smaller R11s, though a bit too thin on the R11s Plus, as it gives it a slight feeling of imbalance when using with one hand.

Unfortunately, the R11s line still comes with a micro-USB port instead of the now-standard USB-C charging port.

The cameras are similar to those on their predecessors, with Oppo sticking to its strengths in photography. The dual 16-and 20-megapixel cameras on the rear deliver clear, detailed photos with good low-light performance.

The range of photography and video options, including the portrait, time-lapse and 4K video shooting modes, gives both phones good versatility.

However, the lack of optical image stabilisation is sorely felt as hand-held videos demonstrate noticeable jitters and shakes.

New to the R11s line is the face unlock feature, which works exactly as it should. It is actually quite speedy and responsive, making unlocking the phone a cinch.

Both phones are still very much iPhone clones in terms of software. Oppo's ColorOS follows the same software design philosophy as iOS, which means there are no app drawers and a shortcut menu is accessed by swiping up rather than swiping down from the notification bar - rather like iOS' Control Centre.

The updated version of ColorOS lets users turn on split-screen multitasking so they can run two apps on the same screen, one above the other - a feature which was missing in the original R11 line.

The phones' battery life remains stellar, lasting more than a day of use. The larger battery of the R11s Plus, in particular, drives its large screen particularly well, giving enough juice to play games and videos, with power to spare at the end of the day.

Oppo used to dominate the mid-range smartphone market with its cheap, well-designed and costeffective phones, but the R11s line has put the last bit - cost-effectiveness - in question.

In particular, the larger R11s Plus comes dangerously close to premium flagship prices without the on-paper specs and performance - at $849, users would expect a better chipset than the Snapdragon 660 found in the device.

The Nokia 8, for example, costs $749, but comes with a high-end Snapdragon 835 processor and similar dual-rear cameras.

•Verdict: The R11s line of smartphones is sleeker and better-looking than the R11 line, with some software enhancements for the same price, but with the same overall performance. But the high price of the R11s Plus might turn away consumers used to Oppo's mid-range pricing.