Anyway, as SPICE goes, I would rank Multisim above LTSpice and Altium, and probably most free or budget packages (which I haven't seen or used, so I don't know for sure). Models using these elements simply aren't compatible, and will require between 'some' and 'a lot' of work to convert. Anyway, PSPICE has its own (incompatible) digital primitives, LTSpice has another, Altium uses SimCode, Multisim uses some other kind of code, etc. The models that aren't, are large (50k+?) and encrypted (usually HSPICE), and require additional licensing to use (e.g., to enable the BSIM3 plugin for someone's transistor-as-in-monolithic-chip-level models). Most models are approximations of the real thing (both for speed and IP-hiding reasons). Talking about digital models is relevant because a lot of manufacturers write models just for one or a few environments, and that's it. Which is fun, because that logic output was driving a gate driver, so the switching circuit was shorted out for a few microseconds there, through no fault of my modeling. I have a lovely screenshot of a simple '74HC04' inverter that received an input voltage, and didn't produce (and propagate) events to the digital model. Just beware of what it is: analog and digital are two different domains, and events can be missed. The logic outputs then have to be updated: another event is scheduled, using the propagation delay. So, if an analog input voltage rises past a logic threshold, that's converted into an event. Whereas analog sim calculates the next timestep based on numerical tolerances, events are scheduled by the timing constraints written into the digital models. Event-driven digital is fundamentally different from analog simulation. (At least as of a few years ago, being that Multisim v10 is the last I used.) It's a basic SPICE environment, so you get analog stuff, XSPICE elements (but they suck, and go largely unused), digital (via event-driven simulation, using some proprietary code - everyone makes their own flavor, because XSPICE sucks at digital), interactive elements, and emulation elements (I think there's 8051 and PIC something in there?).

Multisim 12 online