A major misconception of MVNOs

We have noticed many users switch to MVNO providers expecting the same exact service as that of the customers of their parent networks or MNOs.

This could not be farther from the truth.

Yes, while you are on the same network as post paid customers:
You can expect similar coverage, however you should not expect even half of the same data speeds.

The reason for this is that at the very minumum, the MNOs have at least 3 levels of priority:

The highest priority is reserved for users with "Premium Data" buckets and have not used them up.

The second priority is for all postpaid customers, including those that used up their Premium Data.

Sometimes there's at least 1-2 priorities below that for all postpaid customers that have are considered "high usage" customers.
These customers are those that use up some level of data hidden in a TOS that puts them either on a lower priority than other postpaid customers.
That is if they are not straight up throttled.

Under this is the priority used for all prepaid customers.

Normally, the higher the priority, the faster one's speeds can be when compared to other customers on lower priorities.
This is especially true when a network is congested in any given area.

Network congestion is usually higher when there are more people actively using their devices.
However, a network can be congested just by having too many devices in the same area powered on, even if not in active use.
This is because even while the phones are in "standby" mode, they still use service / data in the background to check for new messages, calls, etc.

Some who have worked on the inside can quote the actual "QCI" numbers assigned to these priority levels.
These numbers are only an internal number used to identify what priority a customer is on.

Many MVNO's tend to be on the same priority level as that of the MNOs prepaid customers.

However, some MVNOs may end up on a priority level even lower than that of the MNO's prepaid customers.

This means many MVNO customers may never see speeds close to what their friends on the respective MNO postpaid accounts.
Some of these MVNO carriers may only be able to offer up to half the speeds of the MNO counterparts.
Others may sometimes get the faster speeds, but the postpaid accounts will always get the priority.

Now while it is true service on MVNOs should be comparable to that of their MNO counterparts, it is unlikely that data throughput would be treated the same. So, the service may be just as good - even if not just as fast.