The SL-1300/1400/1500 (MkI) were a series of the same design sporting full auto/semi auto and full manual versions.
They were replaced with their MkII versions in the process.
At the same time there was the 1600/1700/1800 series and again they were replaced with MkII versions later.
I have a couple of 1300/1500 TTs and they are capable performers. They all have a similar design flaw (IMHO) and that's a rigid plinth with not enough isolation. The 1200MkII is similarly built (rigid plinth) but adds better feet and a large and heavy rubber bottom in the chasis to help isolation. The 1300 is too lightweight.
BTW, the MkII versions are suspended designs (the platter, motor and tonearm assembly are floating on adjustable springs), which usually helps the isolation from the environment. They are also better built.
The MkII designs have a serious flaw in the tonearm section where a complex piece of plastic fails and with it the cue mechanism fails as well. Auto return and full automation goes as a result. But a new piece has been finally designed in 3D sketch and can be ordered from a website that 3D-prints them so that problem is solved (with some skills and care).
I also have a few 1300 MkII TTs and I can offer you comparative info:
From the looks side, I'm a fan of the MkII design and looks. Mostly I like the platter without strobe engravings. It was too cliche in the 80s to have such strobe dots and the MkII did away with them. They are there, under the platter and visible from a small cutout window so the function is still there - not that you really need it.
The MkI are FG (not Quartz Locked) so there's a small deviation to be expected from time to time. The speed adjustment trimmers are to be used periodically. So they need to be clean. Extra clean. Expect to have to de-oxit them as well as their counterparts on the speed control pcb. Once they are clean the deck performs excellently. If they are dirty (usually are after so many years) it gives good cause for a low selling price (which is good).
The tonearm is pretty basic but (as someone wrote) Technics Tonearms, even the basic ones, were way better than some of the well known ones, both in geometry and in friction (lateral and vertical).
If you want to go for a better tonearm you need to find an SL1600/1700/1800 MkII, which are suspended sub-chasis design and share the same tonearm with the SL1200MkII. The SL-1800MkII, being fully manual, has even the same looks on the tonearm (cue lever rather than cue button in the front). The 1300MkI tonearm has no VTA adjustment. The 1300mKII tonearm has VTA adjustment by means of a slider mechanism and a securing screw at the side. Crude but effective (you need to put the tonearm in the resting place and do the adjustment). The 1600MkII share the same feature with the 1200MkII. The VTA is adjusted by means of a rotating ring at the base of the tonarm. You can easily adjust VTA while playing a record. Very handy and that's the way I like. I doubt you will find any tonearm outside these to offer such a feature.
Considering my experience with the entire range, I would say that the SL-1500MkI is a fine workhorse of a table. Fully manual so you don't have to fiddle with the automation mechanism if it fails (mainly some careful cleaning of hardened lube, adjustment and careful re-lubing). The SL-1300 is also a good contender if you like full auto. I know I do sometimes so I enjoy my SL-1300MkII more than the SL-1200MkII. Once can strip down a 1500 into the components (without desoldering anything), clean up everything (including washing the plinth if needed) an then put everything back together in about an hour.
The 1300 and 1500 can be tweaked by putting modelling clay inside the plinth, mostly to the empty space between the bottom cover (plastic) and top part (aluminum) to enhance mass and vibration reduction. It can also take most carts (except perhaps the highest compliance once; it can take them but with some LPs it will not behave as good as it should). Generally that's not an issue as Shure V15-IV MR and the likes are not available any longer. I've successfully tried a Shure M97xE on a 1500 with the brush down. It performed so well.
How do the 1300/1500 perform compared to other TTs from other manufacturers? Not bad at all. Technics made a name with their direct drive TTs and the entire range is above average.
From a collectors point of view, I would jump to a single owner 1300 that came complete with accessories and the original box. The price isn't bad also. For $100 it would be a score, I think.
