There are multiple practical reasons where five ORs of bandwidth X MB/s each could be superior to one OR of bandwidth 5X MB/s. There are some restrictions and exceptions to this point in general. This list is not meant to be the comperhensive list of all possible advantages and/or disadvantages, but give you enough clue to get the idea. Let us start and list some of them:

1. ***Down times***

Any system would have down time for varaity of reasons. Five distributed system is much less prone to catastrophic failure than one centeral system. This is straight out of a basic reliability manual. In this case at down times Lucy would have zero probability of success, while Bob would have some probability of success. This assume all five systems will not go down simultaneously.

2. ***Distribution***

It is clear that one 5X system can be located at a single location, while five systems can be distributed worldwide. One scenario may look at distribution of relays worldwide and distribute the five relays at top five locations that relays are located at (Germany, France, US, etc.). Now the attacker can make sure that folks who may reject certain locations due to their conviction, still have a chance of falling into trap.

3. ***Efficency***

Having 5X amount of bandwidth does not necessasirly means that it is fully being utilized. 
If anybody for any reason suspect an specific relay or a country that a given relay is located at, it maybe avoided. This can go to  point that the relay is no longer working efficiently. Distributing the system to several smaller one at different locations and under different names will alleviate this problem. In addition each relay can be configured to accept or reject specific tasks independently. This make the analysis of data much faster. 

In Short it is not enough to produce a 5X MB/s relay. One need to gain the trust or at least the perceived trust of Tor and its users to be efficiently effective attacker (or non attacker for that matter). This can be facilitated by starting large number relays rather than small number of relays even at constant capacity.

Obviously, there maybe a cost disadvantage to running multiple relays even at constant capacity.

Some of the restrictions and exceptions to this analysis are:

1. The total bandwidth should not be so low that when you divide it to several parts it become unusable. I believe, if not mistaken, that minimum advisable relay bandwidth per Tor guidlines is currently about 250 kB/s.

2. The cost analyis should not be so prohibitive that make this exercise untenable. If you can increase the capacity with some of this cost you may do so and make  the best compromizes.