Confused about speeding up a video

[nnamerz]

I have some CCTV recordings that I would like to speed up (like a timelapse) and I am confused about which method to use. I tested Avidemux and VSDC Video Editor and they both speed up videos in different ways: 
•The "Change FPS" filter in Avidemux appears to speed up a video by cramming in more frames per second. 
•The "Speed (%)" setting in VSDC appears to speed up the video by discarding extra frames, but keeps the final frame rate the same as the original file.

Is one method better or preferred over the other? Are there any major pros/cons for each method?

Here are the "MediaInfo" results for an MP4 test file I sped up by 10x using both methods:

ORIGINAL FILE 
FILE SIZE/LENGTH: 37 MiB / 1 min 7 s 134 ms [00:01:07.134 (00:01:07:03)] 
VIDEO BITRATE/FPS: 4 678 kb/s () @ 15 FPS (Constant) [Total Frames: 1008] 
SIZE/ASPECT: 1920px * 1080px @ 16:9 (1.778) Aspect Ratio 
VIDEO FORMAT: AVC (Advanced Video Codec) / High@L4 / CABAC / 1 Ref Frames 
VIDEO CODEC: video/H264 / Advanced Video Coding / 8 bits / Progressive Scan 

VSDC (Changed speed from 100% to 1000%  to speed up by 10x) 
FILE SIZE/LENGTH: 14 MiB / 6 s 734 ms [00:00:06.734 (00:00:06:11)] 
VVIDEO BITRATE/FPS: 17.0 Mb/s () @ 15 FPS (Constant) [Total Frames: 101] 
SIZE/ASPECT: 1920px * 1080px @ 16:9 (1.778) Aspect Ratio 
VIDEO FORMAT: AVC (Advanced Video Codec) / High@L5.1 / CABAC / 3 Ref Frames 
VIDEO CODEC: video/H264 / Advanced Video Coding / 8 bits / Progressive Scan 

AVIDEMUX (Changed FPS from 15 to 150 to speed up by 10x) 
FILE SIZE/LENGTH: 17 MiB / 6 s 727 ms [00:00:06.727 (00:00:06::9)] 
VIDEO BITRATE/FPS: 20.0 Mb/s () @ 150 FPS (Constant) [Total Frames: 1009] 
SIZE/ASPECT: 1920px * 1080px @ 16:9 (1.778) Aspect Ratio 
VIDEO FORMAT: AVC (Advanced Video Codec) / High@L5.2 / CABAC / 4 Ref Frames 
VIDEO CODEC: video/H264 / Advanced Video Coding / 8 bits / Progressive Scan 

[szlldm]

You should use a "Resample FPS" filter after "Change FPS", to reduce FPS (while keeping the duration). This could improve re-encoded quality at the same output size (or same quality with smaller files).

[nnamerz]

You should use a "Resample FPS" filter after "Change FPS", to reduce FPS (while keeping the duration). This could improve re-encoded quality at the same output size (or same quality with smaller files).

Would using both these filters together end up giving me a similar result to what VSDC outputs? Or is VSDC doing something completely different?

[szlldm]

Would using both these filters together end up giving me a similar result to what VSDC outputs?

yes