The short answer
It makes no difference to the reading.
A chart is a fixed object. It is calculated from a birth date, a birth time and a birth place, and none of those change depending on whether the conversation happens in a room, on a video call, or over the phone.
Anyone charging a premium for an in-person session on the grounds that it is more accurate is charging for something that does not exist. If that claim is made to you, it is worth noticing what else they might be willing to say.
Why most consultations are online
Practicality, not preference.
Clients are in the UK, India, the Gulf, North America and Australia. A method that required everyone in one room would exclude most of the people asking, and it would do so for no methodological reason.
There is also a smaller and more human reason. A great many of the questions people bring are ones they would rather ask from their own kitchen than across a desk: a marriage under strain, money that is not holding, a worry about a child. People are noticeably more direct on a video call from home, and directness makes the session better.
The three differences that actually matter
None of them is about accuracy.
1. Recording and notes
Online sessions are trivially easy to record if you ask beforehand. In person you are relying on your own notes while also having the conversation.
In practice this matters less than people expect, because a written summary of the main chains and the timing discussed can be sent afterwards either way. Most people find that more useful than a recording they never replay.
2. Scheduling
Online is more flexible, particularly across time zones, and easier to rearrange if something comes up.
In person means a fixed time and travel at both ends, which for a one-hour conversation is often the larger commitment.
3. Whether anyone needs to see a space
This is the one genuine exception, and it applies to property rather than to charts.
A Vastu and property consultation works from a floor plan and an accurate compass orientation, both of which you can supply remotely. For a standard flat or house that is usually sufficient.
For an unusual building, a commercial premises, or a plan you are not confident about, a visit can genuinely add something, because orientation is the most common source of error in a self-measured assessment and it is easier to get right in person.
Everything else about a property reading, including reading the findings against the occupants' charts, works identically at a distance. Should I buy this house sets out what an assessment actually covers.
What is not required, either way
Worth stating plainly, because some practices imply otherwise.
Your photograph. Nothing in this method reads appearance.
Your presence in a particular place. No location is more auspicious for a conversation than another.
Your palm, your signature, or an object of yours. Those belong to other practices. If a chart reading asks for them, ask why.
The inputs are your birth details and the dates of past events, and neither travels better in one direction than the other.
Which to choose
Choose on convenience, honestly.
Online or phone if you are outside the UK, if scheduling is tight, if you would rather have the conversation from home, or if you want it recorded easily. This is what most people choose and it is the default.
In person if you strongly prefer talking to someone in a room, or if the subject is a property with a plan you are unsure about.
Phone rather than video if you would rather not be on camera. Nothing visual is required, and some people are noticeably more open without a screen. It is a perfectly normal request.
What does affect the quality
Since the medium does not, it is worth naming the things that do.
The accuracy of your birth time, which matters more than anything else. Why birth time accuracy matters explains the mechanism, and if you do not know it, I do not know my birth time covers what changes.
Whether you bring dated past events, which is what lets the chart be checked before anything is said about the future.
Whether you have written your questions down, because people forget the real one under the pressure of the moment.
All three are covered in how to prepare for a reading, and all three matter considerably more than the room.
Booking
Consultations run in English or Hindi; say which you prefer when you book. Say also whether you want video or phone, and whether you would like the session recorded.
The BNN birth chart reading and the focused readings are all available either way, and what actually happens in a consultation describes the session itself, including what will not be said in it.