GetAllDetectorData() and GetAllDetectorDataSafe() are both methods that can be used to retrieve detector data for a specified detector object. 

1. The main difference between the two methods is that GetAllDetectorDataSafe() returns a two-dimensional array of double values double[,] that contains all the detector data for the detector object, while GetAllDetectorData() returns a boolean value that indicates whether the detector data was retrieved successfully, and one-dimensional array double[] .
2. GetAllDetectorDataSafe() does not require the input of numPixels and detectorData, whereas GetAllDetectorData() requires these parameters in addition to (detector) ObjectNumber and Data(type).

Check the examples to use the two methods: 

For python: 

1TheNCE = TheSystem.NCE
2DetObj = 4
3obj = TheSystem.NCE.GetObjectAt(DetObj);
4numXPixels = obj.ObjectData.NumberXPixels;
5numYPixels = obj.ObjectData.NumberYPixels;
6
7DetRectangleData_FluxArea = TheSystem.NCE.GetAllDetectorDataSafe(4, 1)
8for x in range(numXPixels):
9    for y in range(numYPixels):
10        print(DetRectangleData_FluxArea[x,y])
11
12numPixels=numXPixels*numYPixels
13detectorData=np.zeros(numPixels, dtype=np.float64)
14bool_value, detectorData= TheNCE.GetAllDetectorData(DetObj, 1, numPixels,detectorData)
15for i in range(numPixels):
16    print(detectorData[i])

For matlab: 

1TheNCE = TheSystem.NCE;
2
3DetObj = 4;
4obj = TheSystem.NCE.GetObjectAt(DetObj);
5numXPixels = obj.ObjectData.NumberXPixels;
6numYPixels = obj.ObjectData.NumberYPixels;
7
8DetRectangleData_FluxArea = TheSystem.NCE.GetAllDetectorDataSafe(4, 1);
9for x = 1:numXPixels
10    for y = 1:numYPixels
11        disp(DetRectangleData_FluxArea(x,y));
12    end
13end
14
15numPixels=numXPixels*numYPixels;
16detectorData=NET.createArray('System.Double', TheNCE.GetDetectorSize(4));
17bool_value=TheSystem.NCE.GetAllDetectorData(DetObj, 1,TheNCE.GetDetectorSize(4),detectorData);
18for i = 1:numPixels
19    disp(detectorData(i));
20end
21
22

In matlab, the retrieved data from GetAllDetectorData() need to be rearranged from 1D array to a matrix, detectorData = flipud(rot90(reshape(data.double, rows, cols)));

and here is a simple example to show the transform: