There isn't a right answer here. Typically your bag will make it, maybe it won't, and that's as scientific as it gets. The usual outcome of delayed baggage is that it gets delayed a few days, sometimes it takes a lot longer. Two big factors here are (a) exactly how big the proposed bags would be and (b) how full the EDI-LHR sector is in particular. This is because EDI will enforce limits on full flights. If the bag is taken off at the gate there is a higher chance of it not making RAK because it will be loose loaded rather than in the container for connections. The usual compromise here is to pack strategically so that anything that gets delayed a few days isn't a big deal or can be easily replaced in RAK. Obviously cross pack bags so that if one bag is delayed one person doesn't get all the problems. Take a photo of contents, add a piece of paper on top of the contents, inside the bag, with contact details and PNRs.