I am planning to buy an oscilloscope. I always used oscilloscopes which come with an LCD display. But I found there are USB oscilloscopes as well which can be connected to PC and get data from the PC. Since I already have a laptop I felt like that's a better choice.
But is there any disadvantage in terms of accuracy/efficiency for USB type?
Although this is a very opinion-based matter, there are two things to keep in mind. I presume here, with "USB scope" you refer to an oscilloscope that has no display or controls, and requires a computer to operate. I presume you do not mean an oscilloscope that can be connected to a computer, since any modern scope is capable of doing this.
USB scopes are often made to a price - they are aimed at entry-level buyers, who consider 500 USD/EUR/Whatever too much. Hence, they will, in my experience, be of lower quality. Exceptions to this exist - I've heard many good things about the picoscope, and of course there are devices such as the NI virtualbench that are excellent products (however I think this is not the price range you had in mind when asking this question).
The main difference is in the interface. In the end, most oscilloscopes are the same (to the untrained eye): Apart from a bandwidth difference between models, digital scopes are just fancy analog-to-digital converters with trigger systems and a screen. But this latter is key: The triggering system, its capabilities, and the software to control the entire thing is what makes-or-breaks an oscilloscope - esp. to someone who is at the knowledge level to ask this question. For every day, hobby use, I much prefer the physical nature of oscilloscope control knobs. Fiddling about with mouse sliders and such just never seems to work fast for quick-and-dirty measurements.
And finally as a sidenote: Consider the lifespan of a product and its dependence on a second system. If you purchase a USB oscilloscope, there is a good chance you won't be able to use it in 10-15 years. No more driver updates, computers (in whatever form they are then) no longer have USB interfaces, the software doesn't support your device, etc.. A "classic" oscilloscope is fully integrated and stand-alone. As long as the thing powers on, you know it will be able to take measurements. You need not rely on the support of the device on a second system.
A USB scope can be useful as a lower cost alternative to a non-USB scope. But it will tie up your laptop if at the same time as testing electronics you wish to look at schematics.
Also be aware that the typical modern standlone LCD screen scope that is in the typical hobbiest or single engineer budget price range is going to have more features that the software than goes with the USB type scopes. One reason for this is that the standalone scope manufacturer is able to protect his software investment whereas if a USB scope manufacturer makes very nice PC based scope software there will be rip-off manufacturers that make clones of their hardware and pirate and distribute the software. (Case in point a constant problem being suffered by the folks that make the Saleae brand if USB logic analyzers).
If you're travelling around a lot, some people prefer a USB oscilloscope. But, if you're spending the majority of your time in the same place, engineers almost universally prefer a stand-alone benchtop scope.
Pros of USB oscilloscopes:
Pros of Benchtop oscilloscopes:
This talked about in more detail in the "5 Common Mistakes People Make When Buying a Low-Cost Oscilloscope" here:
https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=2830640
