I'm shopping for a new bass and I am think about 3 different choices.
I play a 5-string now and want to experiment with a 4-string to see if i'd rather stick to 4.
any tips?
Giving up playing a real* bass? Well, I'm not going to be very sympathetic! Usually that is a sign that you really aren't taking full advantage of the 5 strings.
* All "real" basses have 5 or more strings...
To my way of thinking, the only reason to go to a 4 string is because you want to retro back to old school. And that immediately limits your choice to the Fender with flatwounds on it. So go for it!
I've got a MIM Jazz deluxe V that is the equal of any American in town. I know because I went around and l played them all. It's active, of course, and the Fender electronics gives wonderful tonal control with the mid knob. It's fretted with flatwounds. I modded it by replacing the second volume with a rotary switch that gives Neck, both parallel, both series, bridge pickup switching. Got it used for a song and it is the equal of any Am. equivalent in tone, looks or playability. It's the old school master! (Yeah 4 strings would be a tad more authentic, but hey I have to make some compromises for my own comfort! Few notice the extra string anyway.)
And yes I own two G&Ls as well. I've got a L-2500 Tribute Fretted in Ash, and a similar L-2500 fretless Am. G&L. As all American made G&Ls the latter has wood to die for. Otherwise both are very similar basses. Both are more modern sounding than the Fender (though I've never put flatwounds on them yet) and the range of controls is amazing in it's sublety. The passive modes really kick serious butt and the fact it has bass and treble controls in passive is a major plus. (You do have to play a bit with the Amp EQ to get them optimized as being passive they don't boost...so you have to add that from the amp) The active boosted highs settings gives a really decent slap tone, but usually I prefer the tone of passive.
The fretless has been left factory, but the Tribute was modded by me to include an additional switch for single coil tone. I love the added clarity of the single coil setting and use it a lot.
Knobs, switches, mods! You can see that if you are one of the "all Jaco needed was a volume control" crowd, you won't get anything out of talking to me! Some people like to search for "their sound" and once they find it, it stays that way forever. No knobs or adjustments ever change. Me, I like the idea of being in control of my tone and matching it to the music. I love lots of knobs and adjustments, but I don't want it to be a nightmare to adjust on the fly like two volumes. So switches are my favorite thing. The G&L settings are so subtle that fine tweaks are a waste of time anyway. Flipping switches is fast and effective.
As you can see, both my Fender and the two G&Ls are very much along the lines of "my" way of playing bass. My rule is usually "better to have it and not use it than to need it and not have it". Although I have recently backed off from 6 strings to the above three basses because my current music doesn't ever really need the extended upper range, so I bent the rule a bit so I can use the G&Ls and Fender.
As for where you are coming from, well that's your decision to make. But you might as well figure out right now that the G&Ls are not your 4 string P bass with only a volume control. But if that is good or bad, only you can decide. For me it's good.