Lot's of useful comments above. Yes, 5 semitones more. Yes, you can radically rethink your approach to fingering, playing across the neck, and shifting. Yes, harder to slap, but no one told me so I didn't know, and thus didn't care.
But wait a minute. Not much discussion of the 44-01 vs 55-01 as basses. I have owned both, and still have my 55-01. I didn't sell the 44-01 because I didn't like it. I sold it because I replaced it with an NYC Sadowsky. I was using the 44-01 for live broadcasts and recording. It was unique among my instruments because it was my only active 4 string instrument. It was also unusual because was it my only instrument pairing an Ash body WITH a Rosewood fingerboard.
I view my basses as tools. I hated selling the 44-01, but I didn't need it--and was glad a friend bought it and really likes it. I kept the 55-01 because it is my only BEADG tuned bass--my other 5er is fretless and is tuned EADGC.
Here are some pics. First is the 44-01 in a photo from Bass Emporium. This is my actual bass as I first saw it on the web. Amazing Ash grain!
The setup on the instrument was great. The neck was a work of art.
Now the 55-01D. It is an unusual bass. They no longer make the D model (Deluxe). I ordered it with 3tsb, quilt, and rosewood fingerboard. Weeks later Lakland informed the dealer that they were discontinued. I was unhappy. The dealer had a 55-01D with a maple FB, and swapped it with the rosewood FB neck off of another Skyline.
I have what is probably the "last 55-01D with a rosewood fingerboard."
I love the feel of the neck. The pickups are Bartolini's and the preamp is the stock Korean Preamp. I have considered upgrading, but somehow can't let go of the stock electronics. This bass has been used for recording and touring, but I found it hard to deal with on live broadcasts because they are in effect one shot live recordings. After preserving a few clams for all eternity, I went back to the musical certainty of using a 4 string--the 44-01 in fact. After the custom P/J arrived, well, you know the rest.
If I had no reason to play 5 string at times, or if I really needed a new "Main Bass" 4-string, I'd get the 44-01. They are wonderful and can be modded "from here until next May."
If I needed a 5er and was not going to need to play it in exposed professional situations, i.e., it's OK if I am not always playing my best as I adjust and learn, then I'd get the 55-01.
IMHO, it is all about what YOU need musically, and what you want to do in terms of your playing. 5 is not better than 4, just different. Ask Victor Wooten.
Pic 55-01D: