Hi! I have one of each - a Python and a Lee's Ultimate - I find that the suction on the Python pump is a bit better although I cannot figure out why as the parts are basically identical.
I find all the other parts of both systems to be entirely adequate and even completley interchangeable! (actually, the lees male and female valvs are a bit easier to add to the tubing). After buying a 50 foot Python (too long for my needs), I realized there was an easier way to get one - buy the parts and get the tubing at the harware store! Or, Buy the Lee's parts and get the tubing at the harware store! I cut the tubing in half, bought the Lees parts, and made an Ulti-vac with Python tubing! Shhh, don't tell Python! (I later bought tubing at the hardware store, bought Python pump and other parts Lees and made a third siphon system - the color coding also helps to prevent cross-contamination as the Python is green, the Lees blue, and the thrid is green and blue)!
When the neck on the Python pump broke (and I had to wait two weeks for a replacement), I substituted a Lees' backup Lee's pump I had - I am now convinced that the Lee's pump does not suction as strongly as the Python as the rest of the system I was using was the Python - this may have something to do with the seal, which looks similar, but may be slightly different in size or quality...

- basically, except for the pump, the rest of the parts seem entirely equal to me so I buy whichever is more economical.
I posted a "recipe" for building a Python or Lee's - or a hybrid - in Product Review under Lee's Ultimate... listing the different brand names for the same parts and which are required to build the "system".
NOTE - I always keep a spare pump becuase they do have a tendency to break with frequent use... if you have a pet store selling them nearby, great! I don't so I keep a spare handy - once, three pet stores, not near by, were all out of the Python pump at once!
BTW - the shorter the length of the tube, the greater your suction will be - if you don't need 50' of tubing, cut it! Keep the spare tubing becasue if you move, you can alwyas rejoin the tube by buying "replacement" connectors and adding them to the tubing, increasing the length of the system. This is exactly the same thing they sell as extensions!
I use a digital thermometer and point the refill near the probe at filling so I can quickly see what temp is coming out of the tap and adjust the hot and cold accordingly. With a standeard thermometer, I used to hold it under the faucet outflow for about 30 seconds until I saw that the temp. ont he thermometer under the faucet matched the temp. of the thermom. in the tank - and then filled.
FANTAIL - Times - when I used the 50 foot Python my 20 g tank, it took about 15minutes (and we have low water pressure). When I cut in half, which I was able to do - maybe your distance requires 50 feet - that time changed to about 9 minutes.
When I use the Lees on the 12g tropi tank it takes about 15 minutes! At 25 feet!
When I used the Lees' pump on the Python system (the pump was new and otherwise would have been steralised) on the 20g, it took about 16 minutes at 25 feet! I was not even sure it was draining... although filling always goes faster.