You are not going to notice too many differences regarding the way that online slot machines play and pay when you compare them to the way that mobile slot machines play and pay, and as such you are never forced to make compromises when playing in either of those two quite different playing environments.
Online slot machines however are going to be accessible to you on a computer or laptop, and as such one thing you will notice is that the screen size will be much bigger than obviously the screen size on a mobile slot game will be.
The control buttons are also going to be much smaller when you are playing slot machines on mobile device and you will be tapping on for example the spin button to send the reels spinning when paying mobile slots instead of clicking onto that button with your mouse when playing online slots.
The long term expected pay-out percentages are comparable on both playing environments too, and if you are playing the same slot machine from the same slot game designed then the long term expected pay-out percentages tend to be the same on both their online and mobile slots.
The stake levels are also going to be just as variable when you are playing online and mobile slots, so do not think you are ever going to be forced to have to play for higher stake when playing in one playing environment compared to the other.
As for you being able to claim bonuses, enter slot playing competitions such as slot tournaments and also getting access to lots of brand new and never seen before slot machines, well you will find just as many promotional deals, slot tournaments and new slot machines in both playing environments too.