Personally, I say let them pick the difficulty. Case in point;
Say there's a store that sells Cyberdecks/Cyberwear/expensive Commlinks/other techy valuables. Now, first obstacle is that right out of the gate they require basic info, background checks for customers, etc. Okay, decent fake SIN can take care of that with a little luck. Next, they have different availability for different levels of gear. Say the basic inventory is street-level, common stuff. Think the basic HTC or Samsung phones the back of a store has in boxes. Decent, make a quick buck on them, but not exactly a huge payday. Those they keep in store at all times because they sell regularly.
Then there's the showcase models. These are the ones they have in the glass cases for display, and while they have some of them in stock to buy, it's a limited inventory. However, they're a step above the regular, run of the mill stuff, something only yuppies with rich parents can usually afford.
And finally, there's the premier model, the creme-De-la-creme, that's the newest hot model. It has all the bells and whistles, newest tech, and is a pricy mo-fo. Everyone wants one. However, the store doesn't keep them in stock, they only order them to buy for individual customers. And to order one, you have to give your usual background info, SIN, etc, but also a downpayment of say something like 10% or so, to ensure you're a serious buyer.
Now, the store itself has regular security, alarms, motion sensors, basic Matrix secuirty firewall, etc. Nothing insane but a decent bit. Additionally, the showcase models are kept in secured display cases that only the store manager and assistant manager have the key to. Those display cases can be cracked, but they're tamper-proof glass, have extra secirity focused on them at night, etc.
The other thing is the area of town. This is a decent store, so this district is patrolled by LoneStar/Knight Errant foot patrols and drones, with regular beat cops driving around in their cars just like regular cities nowadays. So basically, they now have a choice.
A) Try to grab the lower-tier models, maybe have a decent operation to scan and wipe the RFID tage from them and try to sell them for a profit. Granted, they have multiple units to sell in order to make any kind of money, which will be harder since they would likely have to find multiple fences, depending how many they steal. Involves getting past street security, overcoming the store security, and grabbing the units without setting off any alarms, plus removing any ID tags and finding a low-level fence.
B) Go for the showcase models. Involves all the same as option A, as well as getting into the tamper-resistant display cases, or into the secure area of the back where they keep them. Again, RFID tags, plus registration numbers on them and such. Fence would have to be low to mid level, since these units are still fairly common but not exactly throwaway or single-use stuff. Might even be worth keeping if any of the PCs can use them as upgrades, though they'd want to scrutinize them for tags, redundant security, etc first.
C) In order to get access to the best of the best the store has requires some legwork. Not only do the PCs have to have someone pose as a potential buyer, his background and fake SIN have to be nearly flawless. Plus he'll need a dummy bank account with funds in it to make a downpayment, or at least a certified credstick with the funds on it. This is where the party face really shines, as the ability to schmooze can really make or break a situation like this. Assuming everything looks good and they order the unit, the PCs will then have to do some checking on the ETA of the unit in order to intercept it, likely on the truck in transit. Otherwise they can try to break into the store afterwards for it, but security might be tightened at this point, depending how suspicious/prudent the manager of the store is.
